14
Tropical Doctor, January 1992
Ultrasound in the diagnosis of parasitic disease Calum N L Macpherson PhD DlC Department of Parasitology. Liverpool School of Tropical "Jedicine. Pembroke Place. Liverpool LJ 5QA. UK rROPICAL DOCTOR.
1992, 22, 14-20
INTRODUCTION
During the last 20 years the application of ultrasonography (US) to clinical medicine has greatly expanded. New and improved (real-time) scanners provide remarkable image resolution and convenient methods of documenting results (video/polaroid/ photographic plate and transparency/thermal printers), There have been no reported side effects with US. The technique is very popular with operators, patients and communities because it is non-invasive and painless. A large number of people can be screened in a short period of time and an instant result is provided. After the initial purchase of the apparatus, which costs from UK £3500 to over £20000, the subsequent running costs are low. What limits the availability of US is the initial nigh capital cost and the need for trained personnel to operate it. These problems can be minimized if a single instrument is shared between departments ar projects. The development of portable scanners over the past decade has facilitated this, and also made it possible to apply US at the community level. Today, US is used in the departments of cardiology, gynaecology, obstetrics, paediatrics, neurology, urology and internal medicine and the technique is being increasingly applied to investigate pathology due to a wide variety of parasitic infections. US is now recognized as a valuable tool for the assessment of morbidity due to parasitic infections at the community level. As the technique is used more frequently for this purpose in different parts of the world, examination methods must be standardized, so that results from different studies can be compared. The aim of this review is to examine the current application of US to parasitic infections. Correspondence to Professor C N L Macpherson. School of Veterinary Medicine. Faculty of Medicine, Eric Williams Medical Science Complex, Champs Fleurs, St Augustine, Trinidad and Tobago
PROTOZOA
A number of protozoan parasites affect organs which are readily imaged by US. Many of the specific pathological effects of these infections cannot, however, be demonstrated by US, because the size of lesions is below the limit of resolution (> 1em), Such parasites include Trypanosoma spp., Leishmania donovani, Giardia intestinalis, and Toxoplasma gondii. US does, however, provide a means of recording the size of an enlarged spleen or liver more accurately than can be done by clinical examination. It is also particularly valuable in the diagnosis of cystic lesions, such as those resulting from infection with Entamoeba histolytica. MALARIA
Malaria is one of the commonest causes of splenomegaly in the world. Clinical examination can only detect a spleen that is enlarged more than 2-3 times normal. Ultrasonography is a useful technique for identifying lesser degrees of splenomegaly, and for estimating the volume of a large spleen more accurately than is possible by clinical examination.
Figure I. Appearance of an amoebic liver abscess due to infection with Entamoeba histolytica. (Photo Dr Lu Yong-Quan}
Tropical Doctor, January 1992 Table 1. Space occupying lesions which may occur in the liver Simple cysts Polycystic liver disease Haemangioma - single/multiple Pyogenic abscess Subphrenic abscess Amoebic abscess - Entamoeba histolytica Hydatid cyst - Echinococcus granulosus/E. multilocularis/
E. vogeli Haematoma Adenoma Hepatocellular carcinoma Hepatic metastases Hepatic lymphoma (focal or diffuse)
An example of the application of US to the study of malaria is a recent investigation of splenic volumes in newborns in malarious and non-malarious parts of Papua New Guinea'. The authors reported that the median splenic volume of infants in malarious areas was double that of infants born in malariafree parts of the country. In neither of the study populations could splenomegaly be detected clinically. Although the significance of these findings is not clear, they reveal an effect of endemic malaria that deserves further study.
15 AMOEBIC ABSCESS
US is as sensitive as radionucleotide scanning, computerized tomography (CT) and magnetic resonance imaging (MRI) for determining the number, location, size and shape of amoebic liver abscesses due to E. histolytica-v (Figure 1). Amoebic abscesses commonly respond to chemotherapy alone (metronidazole), and recently US has been used to examine the time-course and pattern of resolution of abscesses after such treatment. In one study the mean resolution time was 2 months for the smallest abscess (1 em) and 20 months for the largest (22 em)", In the initial diagnosis of amoebic liver abscess, US can detect much earlier and smaller lesions than it is possible to identify by physical examination. Such lesions must be differentiated, with the help of amoebic serology, from other cystic lesions which also occur in the liver (Table 1). In highly endemic areas - eg northern Tanzania" - community based US surveys could be used to help examine the local epidemiology of the disease. HELMINTHS
A wide variety of helminth infections of man produce pathological changes, particularly in the liver, kidneys and bladder, which can be visualized
Table 2. Uses of ultrasound in helminth infections Monitoring Diagnosis
Treatment
Collection of prevalence data
Kidney/bladder Liver Liver Biliary system Biliary system Biliary system Liver /biliary
X X X X X X X
X X X
X X X
Liver/spleen/kidney/ orbit/superficial Liver Liver Orbit/subcutaneous
X X X X
X X
X X
0
0
Liver Liver Subcutaneous/internal tissues/intra-muscular
X
X
Parasite species
Location of pathology
Trematodes Schistosoma haematobium S. mansoni S. japonicum Opisthorchis viverrini O. sinensis O. felineus Fasciola hepatica Cestodes Echinococcus granulosus
E. multilocularis E. vogeli Taenia solium Nematodes Ascaris lumbricoides Toxocara canis Onchocerca volvulus X = proven usage o = potentially useful
X
16
using US. In addition to individual and community diagnosis US has been applied to examination of changes of lesions over time, following surgery and during and after chemotherapy (Table 2). TREMATODES: SCHISTOSOMIASIS
There is growing emphasis to control morbidity and organ damage in schistosomiasis endemic areas. In the field this has historically been evaluated clinically. Although clinical and laboratory data remain essential for the correct diagnosis of schistosomiasis, US is rapidly becoming the preferred field and hospital-based method for detecting pathological lesions and as a means of assessing changes in affected organs following chemotherapy. The increased appreciation and use of US has necessitated the standardization of reporting observations by different investigators in different endemic settings in order to facilitate comparison of results and to more accurately assess longitudinal studies", Schistosoma haematobium Demonstration of pathological lesions (in kidneys, ureters and bladder) due to S. haematobium by US has meant the virtual replacement of contrast injections and pelvic irradiation for intravenous urography. US is now considered to be the imaging technique of choice for detecting uropathy due to schistosomiasis in hospitals as well as in the field. In community-based surveys US detectable pathology was found to be more common in children than adults and was correlated with intensity and prevalence of infections:". In a number of longitudinal studies, US has been used to examine the resolution of uropathy following chemotherapy. Most patients investigated showed a high rate of improvement'P''!". With the current emphasis on controlling morbidity, it is likely that US will play an increasingly important role in determining retreatment intervals, based on the recurrence of morbidity. Schistosoma mansoni Demonstration of pathological lesions due to S. mansoni can be achieved using several different imaging techniques. Because of its sensitivity, specificity and simplicity, US has virtually replaced open wedge biopsy of the liver as the 'gold standard' for detecting schistosomal periportal fibrosisI 5, 16 . Homeida et al. 17 produced a classification of periportal fibrosis based on US appearances, and Doehring et al. 18, 19 devised a system for the staging
Tropical Doctor, January 1992
of hepatic fibrosis by US in children. In these studies a correlation was found between the degree of periportal fibrosis and the size of the spleen, but fibrosis did not correlate with either egg output or liver size!", Gastrointestinal bleeding from oesophageal varices is one of the most serious complications of infection with S. mansoni and recently US has been used to identify hepatic fibrosis in patients with this syndrome-", In some studies US has been used to examine the resolution of hepatic lesions following chemotherapy for S. mansoni infection-'. Reduction in fibrosis can be demonstrated 7 months after the administration of praziquantel-'. In some patients, however, there is a progression of disease; US may be useful in the further study of this phenomenon and in the evaluation of alternative forms of treatment. Schistosoma japonicum The pathological features of the liver in patients with S. japonicum are characteristic: there may be a 'network' of 'fish scale pattern'23,24 or a display of hyperreflective nodules-'. TREMATODES: OPISTHORCHIASIS
Opisthorchis sinensis (formerly Clonorchis sinensis), the 'Chinese liver fluke' occurs in most of Asia east of and including the Indian subcontinent. O. viverrini occurs in the Far East. Both are zoonoses, the dog and cat serving as occasional and reservoir hosts respectively. Humans acquire infection by ingestion of raw or partly-cooked fish, and the young flukes reach the liver via the bile ducts. Damage is caused by the cuticular spines of the young flukes abrading the bile ducts causing thickening. Opisthorchis infections are very common in endemic areas; most infections are asymptomatic, but some patients develop hepatobiliary disease or cholangiocarcinoma, both of which are readily demonstrated by US26,27. O. felineus is an occasional parasite of humans and US has been useful in identifying hepatobiliary lesions-", TREMATODES: FASCIOLIASIS
Fasciola hepatica Fascioliasis due to infection with Fasciola hepatica occurs world-wide. US has been found to be useful in diagnosing lesions secondary to infection with this parasite. Although they are relatively large, the individual flukes cannot yet be visualized with ordinary US scanners-",
Tropical Doctor, January 1992
Figure 2. Use of an ophthalmological real-time scanner to visualize a T. solium cyst in the orbit. The scolex of the parasite can be clearly seen (arrowed) (Photo Dr Eduada Moragrega) CESTODES: CYSTICERCOSIS
Cysticercosis is a major parasitic problem in Central America and northern South America (Mexico, Honduras, Peru, Venezuela and Guatemala), China, south and west Africa and non-Islamic southeast Asia including parts of New Guinea. Sporadic outbreaks occur in the USSR and Spain. In Mexico autopsy studies have shown that subcutaneous cysticercosis affects 2-4% of the population; between 70/0 and 10% of all admissions to neurological wards are due to neurocysticercosis. Cysts due to T. solium vary in diameter between 0.5 cm and I em. They are most frequently located in striated muscle, subcutaneous tissues, the brain parenchyma or the eye. US has a limited value in cysticercosis, because the lesions causing the most important clinical problem, neurocysticercosis, are intra-cerebral and therefore cannot be visualized by US. High resolution ophthalmological scanners have been used to identify orbital cysticercosis (Figure 2). Subcutaneous cysts can be detected by simple palpation, and US provides little additional information of clinical value.
17 application of the technique in medicine3 I •32• US revolutionized the diagnosis of intra abdominal hydatidosis, which previously could only be made at laparotomy. (In the abdominal site, cysts cannot be seen on X-ray unless they are calcified.) An accurate diagnosis of CHD can be made if the characteristic daughter cysts or laminated membrane can be visualized'? (Figure 3). With the recent improvements in the sensitivity and specificity of the ELISA test 30 , all proven and suspected cases of CHD should be confirmed serologically. US is useful for monitoring the response of cysts to treatment'! and changes in cyst size and appearance over time36 • Portable US has been particularly useful in several countries (Kenya, Ethiopia, Sudan, Tanzania, Tunisia, Libya, Uruguay and China) where CHD is endemic. The application of US in these settings has shown that the distribution of hydatid disease is often focal. It has highlighted the importance of the disease in many geographical areas and indicated those territories where control measures would be worthwhile". The development of a rapid (20 min) field applicable dot-blot ELISA has facilitated the concurrent collection of US and serological prevalence data. In addition to obtaining prevalence data, US is a valuable technique for monitoring a control programme, as has been done in the Turkana project in Kenya'",
CESTODES: HYDATIDOSIS
Echinococcus granulosus Cystic hydatid disease (CHD) due to infection with Echinococcus granulosus is the most geographically widespread and medically and economically important clinical disorder caused by a cestode. The value of US in the diagnosis of hepatic CHD has been recognized since the earliest days of the
Figure 3. Unilocular CHD due to Echinococcus granulosus with characteristic laminated membrane (arrowed)
Tropical Doctor, January 1992
18
Echinococcus multilocularis The second most frequent form of hydatidosis is alveolar hydatid disease (AHD) caused by E. multilocularis. This cestode is limited to the Holarctic and presents as a chronic disease in humans, who are aberrant hosts (the parasite causes a rapidly developing and fatal disease in its normal wild rodent intermediate hosts). Over 980/0 of all the primary lesions of alveolar hydatid disease are located in the liver, metastases being reported occasionally in the heart, lung and brain. US has been found to compare favourably with CT for diagnosing the condition. The characteristic features on US and CT have been described by a number of authors (reviewed in ref 39). In the majority of cases parasitized liver tissue appears on US as areas of hyperreflectivity without well-defined limits. Lesions are single, multiple or extensive throughout most of the liver. Parasitized areas are heterogeneous and may contain microcalcifications, the presence of which suggest the diagnosis. Early infections may appear as small 'raised' lesions which may be single or multiple; these are relatively simple to detect, but they may be difficult or impossible to differentiate from metastatic malignant deposits. A diagnosis of alveolar hydatid disease should therefore always be confirmed immunologically. Most people (>98%) with active alveolar hydatidosis have diagnostic levels of specific IgG antibody in their plasma. Serological diagnosis is therefore more straightforward than it is for cystic hydatidosis"; Advanced E. multilocularis lesions may produce either a 'hailstorm' or mottled ultrasound picture. There
.~~"" ...,.V"'lu5 ureguuu'
necrotic area
uuraer co me non reflective
irregular non reflective without proper walls (Figure 4). A recent community-based survey in western China demonstrated the feasibility of using US, in conjunction with serology, for mass screening for alveolar hydatid disease in a highly endemic area (Craig, Liu Deshan and Macpherson, in preparation). US changes may also be used for monitoring the effect of chemotherapy, although changes are not as rapid or as clearly visualized as they are in cystic hydatid disease.
Echinococcus vogeli A rare form of hydatidosis is polycystic hydatid disease (PHD) caused by E. vogeli, which is restricted in its geographical distribution to Central and South America. Sonography has been used for the diagnosis of this parasite", which produces large, polycystic fluid-filled cysts primarily in the liver. The sonographical features have not yet been described in detail. NEMATODES: ONCHOCERCIASIS
Onchocerca volvulus infects over 17 million people in a rather patchy distribution throughout Africa, South and Central America and in the Yemen. The adult worms reside in nodules (onchocercomata) which measure between 0.2 em and 8 em in diameter. Nodules usually occur in superficial, subcutaneous sites and can be detected by palpation; a proportion of these may be misidentified and a number of nodules are buried too deep in the tissues to be detected by simple palpation. US has been used for detecting non palpable onchocercomata'-. In the past, instruments had insufficient resolution to allow the internal structural details of nodules to be seen. Recently a number of workers have used high resolution ophthalmological US scanners to demonstrate the characteristic internal features of nodules (homogeneous echogenicity with small echodense particles and a lateral acoustic shadow)43.44. The higher frequency probes used by Leichsenring et 01. 44 can detect nodules in all locations except those obscured by bone or gas, but the screening procedure takes a long time and would not be applicable for screening surveys. Since US can distinguish between worms, fibrosis and necrosis within superficial nodules, it provides a useful method for monitoring the effect of chemotherapy and has been used for monitoring the in vivo effect of a new macrofilaricide, amocarzine" (CGP 6140). US has also been used to visualize lesions due to Ascaris lumbricoides and Toxocara canis but with
Tropical Doctor, January 1992 currently available equipment the technique is unlikely to be of much clinical importance in these infections.
19
14
CONCLUSION
The full potential of US has yet to be realized. With improvements in the resolution, and with reduction in the capital cost of the equipment, it is likely to be a technique that is increasingly utilized, both for individual diagnosis and for community surveys of parasitic disease. REFERENCES
I 2 3 4
5
6
7
8
9
10 11
12
13
Corkill JA, Brabin BJ, Macgregor DF, Alpers MP, Milner ROO. Newborn splenic volumes vary under different malaria endemic conditions. Anch Dis Child 1989;64:541-5 Terrier F, Becker CD, Triller JK. Morphologic aspects of hepatic abscesses at computed tomography and ultrasound. Acta Radiol Diagn (Stockh) 1983;24:129-37 Ahmed L, Salama ZA, EI Rooby A, Strickland GT. Ultrasonic resolution time for amoebic liver abscess. Am J Trop Med Hyg 1989;41:406-10 Macpherson CNL, Kilama WL, Kihamia CM. Miscellaneous parasitic infections. In: Mwaluko GMP, Kilama WL, Mandara MP, Murru M, Macpherson CNL, eds. Health and Disease in Tanzania London: Harper Collins, 1991 World Health Organisation. Proposal for a practical guide to the standardized use of ultrasound in the assessment of pathological changes. 1991. WHO document No.: TDR/SCH/ULTRASON/913 Degremont A, Burnier E, Meudt R, Burki A, Schweizer W, Tanner M. Value of ultrasonography in investigating morbidity due to Schistoma haematobium infection. Lancet 1985;1:662-5 Doehring E, Ehrich JHH, Reider F, Dittrich M, SchmidtEhry G, Brodehl J. Morbidity in urinary schistosomiasis: relation between sonographical lesions and pathological urine findings. Trap Med Parasit 1985;36:145-9 Burki A, Tanner M, Burnier E, Schweizer W, Meudt R, Degremont A. Comparison of ultrasonography, intravenous pyelography and cystoscopy in detection of urinary tract lesions due to Schistosoma haematobium. Acta Trop 1986;43:139-51 Heurtier Y, Lamothe F, Develoux M, et al. Urinary tract lesions due to Schistosoma haematobium infection assessed by ultrasonography in a community based study in Niger. Am J Trop Med Hyg 1986;35:1163-72 Doehring E, Ehrich HH, Bremer HJ. Reversibilityof urinary tract abnormalities due to Schistosoma haematobium infection. Kid Int 1986;30:582-5 King CH, Lombardi G, Lombardi C, et al. Chemotherapybased control of schistosomiasis haematobia. 2. Metrifonate versus praziquantel in control of intensity and prevalence of infection. Am J Trop Med Hyg 1988;39:295-305 Devidas A, Lamothe F, Develoux M, Mouchet F, Sellin B. Ultrasonographic assessment of the regression of bladder and renal lesionsdue to Schistosoma haematobium after treatment with praziquantel. Ann Soc Belg Med Trop 1989;69:57-65 Hatz C, Mayombana C, de Savigny D, et al. Ultrasound scanning for detecting morbidity due to Schistosoma haematobium and its resolution following treatment with
15
16
17
18
19
20
21
22
23 24
25 26
27
different doses of praziquantel. Trans R Soc Trop Med Hyg 1990;84:662-5 Laurent C, Lamothe F, Develoux D, Sellin B, Mouchet F. Ultrasonographic assessment of urinary tract lesions due to Schistosoma haematobium in Niger after four consecutive years of treatment with praziquantel. Trop Med Parasitol 1990;41:139-42 Homeida M, Abdel-Gadir A, Cheever A, et al. Diagnosis of pathologically confirmed Symmers' periportal fibrosis by ultrasonography; a prospective blinded study. Am J Trop Med Hyg 1988;38:86-91 Abdel-Waheb MF, Esmat G, Milad M, Abdel-Razek S, Strickland G. Characteristic sonographic patterns of schistosomal hepatic fibrosis. Am J Trop Med Hyg 1989;40:72-6 Homeida M, Ahmed G, DaFalla A, et al. Morbidity associated with Schistosomamansoni infection as determined by ultrasound: a study in Gezira, Sudan. Am J Trop Med Hyg 1988;39:196-201 Doehring-Schwerdtfeger E, Abdel-Rahim 1M, MohamedAli Q, et al. Ultrasonographical investigation of periportal fibrosis in children with Schistosoma mansoni infection: evaluation of morbidity. Am J Trop Med Hyg 1990; 42:581-6 Doehring-Schwerdtfeger E, Mohamed-Ali G, Abdel-Rahim 1M, et al. Sonornorphological abnormalities in Sudanese children with Schistosoma mansoni infection: a proposed staging-system for field diagnosis of periportal fibrosis. Am J Trop Med Hyg 1989;41:63-9 Davidson RN, Houston S, Kiire CF. Schistosomal periportal fibrosis in Zimbabwe: use of ultrasound in patients with oesophageal varices. Trans R Soc Trop Med Hyg 1991; 85:380-2 Homeida MA, DaFalla AA, Kardaman MW, et al. Effect of antischistosomal chemotherapy on the prevalence of Symmers' periportal fibrosis in Sudanese villages. Lancet 1988;11:437-40 Mohamed-Ali Q, Doehring-Schwerdtfeger E, Abdel EIRahim 1M, et al. Ultrasonographical investigation of periportal fibrosis in children with Schistosoma mansoni infection: reversibility of morbidity seven months after treatment with praziquantel. Am J Trop Med Hyg 1991;43:444-51 Murakami H. Image diagnosis of schistosomiasis japonica. Comparison of ultrasonigram with CT image. J Kurume Med Ass 1986;49:458-74 Hirata M, Uno M, Iida H, Uno S, Tsutsumi H, Uto K. Serological evaluation of ultrasound examination for chronic schistosomiasis japonica in a previously endemic area - the Chikugo River Basin, Japan. Ann Trop Med Parasitol 1988;82:475-80 World Health Organisation. Data collection and data analysis in a population with Schistosoma japonicum infection. MPH/WHO document, 1988 Elkins DB, Haswell-Elkins M, Mairiang E, et al. A high frequency of hepatobiliary disease and suspected cholangiocarcinoma associated with heavy Opisthorchis viverrini infection in a small community in north-east Thailand. Trans R Soc Trop Med Hyg 1990;84:715-19 Pungpak S, Sommani S, Sunthara Samai P, Vivatanasesth P. Ultrasonographic study of the biliary system in opisthorchiasis patients after treatment with praziquantel. Southeast Asian J Trop Med Pub Hlth 1989;20: 157-62
20 28 Bronshtein AM, Mironov SP, Silaev AV, Panteleeva EIA. Radionucleotide and sonographic diagnosis of lesions of the hepatobiliary system in opisthorchiasis. Med Parazitol (Mosk) 1989;5:13-17 [in Russian] 29 Chen MG, Mott KE. Progress in assessment of morbidity due to Fasciola hepatica infection: a review of recent literature. Trop Dis BullI99O;87:RI-R38 30 Rogan MT, Craig PS, Zeyhle E, Romig T, Lubano GM, Deshan L. Evaluation of a rapid dot-ELISA as a field test for the diagnosis of cystic hydatid disease. Trans R Soc Trop Hyg 1991;85(in press) 31 King DL. Ultrasonography of echinococcal cysts. J Clin Ultrasound 1973;1:64-7 32 Vicary FR, Cusick G, Shirley 1M, Blackwell RJ. Ultrasound and abdominal hydatid disease. Trans R Soc Trop Med Hyg 1977;71:29-31 33 Macpherson CNL, Romig T, ZeyhleE, Rees PH, Were lBO. Portable ultrasound scanner versus serology in screening for hydatid cysts in a nomadic population. Lancet 1987; 1:259-61 34 Craig PS, Zeyhle E, Romig T. Hydatid disease: research and control in Turkana, 11. The role of immunological techniques for the diagnosis of hydatid disease. Trans R Soc Trop Med Hyg 1986;80:183-92 35 Cossetto B, Gruenewald S, Antico V, Little lH. Albendazole treatment of recurrent hydatid disease: serial evaluation with ultrasound. Aust N Z J Surg 1989;59:933-6 36 Romig T, Zeyhle E, Macpherson CNL, Rees PH, Were lBO. Cyst growth and spontaneous cure in hydatid disease. Lancet 1986;ii:861 37 Macpherson CNL, Spoerry A, Zeyhle E, RomigT, Gorfe M. Pastoralists and hydatid disease: an ultrasound scanning prevalence survey in East Africa. Trans R Soc Trop Med Hyg 1989;84:243-7 38 Macpherson CNL, Wachira T, Zeyhle E, Romig T, Macpherson C. Hydatid disease - Research and control in Turkana, Kenya, IV. The control programme. Trans R Soc Trop Med Hyg 1986;80:196-200 39 Didier D, Weiler S, Rohmer P, et al. Hepatic alveolar echinococcosis: correlative US and CT study. Radiology 1985;154:179-86 40 Gottstein B, Tschudi K, Eckert r, Ammann R. Em2-ELISA for the follow-up of alveolar echinococcus after complete surgical resection of liver lesions. Trans R Soc Trop Med Hyg 1989;83:389-93 41 D'Alessandro A, Rausch RL, Cuello C, Aristizabal N. Echinococcus vogeli in man, with a review of polycystic hydatid disease in Colombia and neighbouring countries. Am J Trop Med Hyg 1979;28:303-17 42 Homeida MA, Mackenzie CD, Williams IF, Ghalib HW. The detection of onchocercal nodules by ultrasound technique. Trans R Soc Trop Med Hyg 1986;80:570-1 43 Poltera AA, Reyna 0, Zea Bores G, Nowellde Arevalo AM, Beltranena F. Detection of skin nodules in onchocerciasis by ultrasound scans. Lancet 1987;1:505 44 Leichsenring M, Troger r, Nelle M, Buttner DW, Darge K, Doehring-Schwerdtfeger E. Ultrasonographical investigations of onchocerciasis in Liberia. Am J Trop Med Hyg 1990;43:380-5 45 Poltera AA, Zea-Flores G, Guderian R, et al. Onchocercidal effects of amocarzine (CGP 6140) in Latin America. Lancet 1991;337:583-4
Tropical Doctor, January 1992
The provision of safe blood - policy issues in the prevention of human immunodeficiency virus transmission C J van Dam MD MSc'* L Fransen MD PhD'
D Sondag-Thull MD PhD 2
'AIDS Task Force, EEC, Brussels and "Service Transfusion Sanguine, Centre Hospitalier Universitaire de Liege TROPICAL DOCTOR,
1992, 22, 20-23
SUMMARY
The AIDS epidemic has focused attention on the constraints and deficiencies present in many blood transfusion services in the developing world. We discuss a variety of options for reducing transfusion-related HIV transmission, and suggest how new transfusion strategies may be implemented. We show that a transfusion service cannot rely solely on the screening of donor blood for anti-HIV antibodies and that a more comprehensive approach is needed. Important components of this approach include donor selection and improved clinical practice, in which blood and blood products are prescribed only when really necessary. INTRODUCTION
The blood borne character of AIDS was detected early in the epidemic, when AIDS in haemophiliacs and children was linked to transfusions of either blood components or bloodt-'. Efforts were made to ensure the safety of transfused blood, although no testing methods were then available. Focus was on the exclusion of donors with the then known high risk behaviours", Today a number of different interventions may contribute to the safety of a blood transfusion service and minimize the contribution of blood transfusion to the transmission of HIV. Options to reduce or prevent transmission of HIV through donor blood fall into four major categories. *Joined since submission the WHO STD Programme, Geneva
Tropical Doctor, January 1992
Ultrasound in the diagnosis of parasitic disease Calum N L Macpherson PhD DlC Department of Parasitology. Liverpool School of Tropical "Jedicine. Pembroke Place. Liverpool LJ 5QA. UK rROPICAL DOCTOR.
1992, 22, 14-20
INTRODUCTION
During the last 20 years the application of ultrasonography (US) to clinical medicine has greatly expanded. New and improved (real-time) scanners provide remarkable image resolution and convenient methods of documenting results (video/polaroid/ photographic plate and transparency/thermal printers), There have been no reported side effects with US. The technique is very popular with operators, patients and communities because it is non-invasive and painless. A large number of people can be screened in a short period of time and an instant result is provided. After the initial purchase of the apparatus, which costs from UK £3500 to over £20000, the subsequent running costs are low. What limits the availability of US is the initial nigh capital cost and the need for trained personnel to operate it. These problems can be minimized if a single instrument is shared between departments ar projects. The development of portable scanners over the past decade has facilitated this, and also made it possible to apply US at the community level. Today, US is used in the departments of cardiology, gynaecology, obstetrics, paediatrics, neurology, urology and internal medicine and the technique is being increasingly applied to investigate pathology due to a wide variety of parasitic infections. US is now recognized as a valuable tool for the assessment of morbidity due to parasitic infections at the community level. As the technique is used more frequently for this purpose in different parts of the world, examination methods must be standardized, so that results from different studies can be compared. The aim of this review is to examine the current application of US to parasitic infections. Correspondence to Professor C N L Macpherson. School of Veterinary Medicine. Faculty of Medicine, Eric Williams Medical Science Complex, Champs Fleurs, St Augustine, Trinidad and Tobago
PROTOZOA
A number of protozoan parasites affect organs which are readily imaged by US. Many of the specific pathological effects of these infections cannot, however, be demonstrated by US, because the size of lesions is below the limit of resolution (> 1em), Such parasites include Trypanosoma spp., Leishmania donovani, Giardia intestinalis, and Toxoplasma gondii. US does, however, provide a means of recording the size of an enlarged spleen or liver more accurately than can be done by clinical examination. It is also particularly valuable in the diagnosis of cystic lesions, such as those resulting from infection with Entamoeba histolytica. MALARIA
Malaria is one of the commonest causes of splenomegaly in the world. Clinical examination can only detect a spleen that is enlarged more than 2-3 times normal. Ultrasonography is a useful technique for identifying lesser degrees of splenomegaly, and for estimating the volume of a large spleen more accurately than is possible by clinical examination.
Figure I. Appearance of an amoebic liver abscess due to infection with Entamoeba histolytica. (Photo Dr Lu Yong-Quan}
Tropical Doctor, January 1992 Table 1. Space occupying lesions which may occur in the liver Simple cysts Polycystic liver disease Haemangioma - single/multiple Pyogenic abscess Subphrenic abscess Amoebic abscess - Entamoeba histolytica Hydatid cyst - Echinococcus granulosus/E. multilocularis/
E. vogeli Haematoma Adenoma Hepatocellular carcinoma Hepatic metastases Hepatic lymphoma (focal or diffuse)
An example of the application of US to the study of malaria is a recent investigation of splenic volumes in newborns in malarious and non-malarious parts of Papua New Guinea'. The authors reported that the median splenic volume of infants in malarious areas was double that of infants born in malariafree parts of the country. In neither of the study populations could splenomegaly be detected clinically. Although the significance of these findings is not clear, they reveal an effect of endemic malaria that deserves further study.
15 AMOEBIC ABSCESS
US is as sensitive as radionucleotide scanning, computerized tomography (CT) and magnetic resonance imaging (MRI) for determining the number, location, size and shape of amoebic liver abscesses due to E. histolytica-v (Figure 1). Amoebic abscesses commonly respond to chemotherapy alone (metronidazole), and recently US has been used to examine the time-course and pattern of resolution of abscesses after such treatment. In one study the mean resolution time was 2 months for the smallest abscess (1 em) and 20 months for the largest (22 em)", In the initial diagnosis of amoebic liver abscess, US can detect much earlier and smaller lesions than it is possible to identify by physical examination. Such lesions must be differentiated, with the help of amoebic serology, from other cystic lesions which also occur in the liver (Table 1). In highly endemic areas - eg northern Tanzania" - community based US surveys could be used to help examine the local epidemiology of the disease. HELMINTHS
A wide variety of helminth infections of man produce pathological changes, particularly in the liver, kidneys and bladder, which can be visualized
Table 2. Uses of ultrasound in helminth infections Monitoring Diagnosis
Treatment
Collection of prevalence data
Kidney/bladder Liver Liver Biliary system Biliary system Biliary system Liver /biliary
X X X X X X X
X X X
X X X
Liver/spleen/kidney/ orbit/superficial Liver Liver Orbit/subcutaneous
X X X X
X X
X X
0
0
Liver Liver Subcutaneous/internal tissues/intra-muscular
X
X
Parasite species
Location of pathology
Trematodes Schistosoma haematobium S. mansoni S. japonicum Opisthorchis viverrini O. sinensis O. felineus Fasciola hepatica Cestodes Echinococcus granulosus
E. multilocularis E. vogeli Taenia solium Nematodes Ascaris lumbricoides Toxocara canis Onchocerca volvulus X = proven usage o = potentially useful
X
16
using US. In addition to individual and community diagnosis US has been applied to examination of changes of lesions over time, following surgery and during and after chemotherapy (Table 2). TREMATODES: SCHISTOSOMIASIS
There is growing emphasis to control morbidity and organ damage in schistosomiasis endemic areas. In the field this has historically been evaluated clinically. Although clinical and laboratory data remain essential for the correct diagnosis of schistosomiasis, US is rapidly becoming the preferred field and hospital-based method for detecting pathological lesions and as a means of assessing changes in affected organs following chemotherapy. The increased appreciation and use of US has necessitated the standardization of reporting observations by different investigators in different endemic settings in order to facilitate comparison of results and to more accurately assess longitudinal studies", Schistosoma haematobium Demonstration of pathological lesions (in kidneys, ureters and bladder) due to S. haematobium by US has meant the virtual replacement of contrast injections and pelvic irradiation for intravenous urography. US is now considered to be the imaging technique of choice for detecting uropathy due to schistosomiasis in hospitals as well as in the field. In community-based surveys US detectable pathology was found to be more common in children than adults and was correlated with intensity and prevalence of infections:". In a number of longitudinal studies, US has been used to examine the resolution of uropathy following chemotherapy. Most patients investigated showed a high rate of improvement'P''!". With the current emphasis on controlling morbidity, it is likely that US will play an increasingly important role in determining retreatment intervals, based on the recurrence of morbidity. Schistosoma mansoni Demonstration of pathological lesions due to S. mansoni can be achieved using several different imaging techniques. Because of its sensitivity, specificity and simplicity, US has virtually replaced open wedge biopsy of the liver as the 'gold standard' for detecting schistosomal periportal fibrosisI 5, 16 . Homeida et al. 17 produced a classification of periportal fibrosis based on US appearances, and Doehring et al. 18, 19 devised a system for the staging
Tropical Doctor, January 1992
of hepatic fibrosis by US in children. In these studies a correlation was found between the degree of periportal fibrosis and the size of the spleen, but fibrosis did not correlate with either egg output or liver size!", Gastrointestinal bleeding from oesophageal varices is one of the most serious complications of infection with S. mansoni and recently US has been used to identify hepatic fibrosis in patients with this syndrome-", In some studies US has been used to examine the resolution of hepatic lesions following chemotherapy for S. mansoni infection-'. Reduction in fibrosis can be demonstrated 7 months after the administration of praziquantel-'. In some patients, however, there is a progression of disease; US may be useful in the further study of this phenomenon and in the evaluation of alternative forms of treatment. Schistosoma japonicum The pathological features of the liver in patients with S. japonicum are characteristic: there may be a 'network' of 'fish scale pattern'23,24 or a display of hyperreflective nodules-'. TREMATODES: OPISTHORCHIASIS
Opisthorchis sinensis (formerly Clonorchis sinensis), the 'Chinese liver fluke' occurs in most of Asia east of and including the Indian subcontinent. O. viverrini occurs in the Far East. Both are zoonoses, the dog and cat serving as occasional and reservoir hosts respectively. Humans acquire infection by ingestion of raw or partly-cooked fish, and the young flukes reach the liver via the bile ducts. Damage is caused by the cuticular spines of the young flukes abrading the bile ducts causing thickening. Opisthorchis infections are very common in endemic areas; most infections are asymptomatic, but some patients develop hepatobiliary disease or cholangiocarcinoma, both of which are readily demonstrated by US26,27. O. felineus is an occasional parasite of humans and US has been useful in identifying hepatobiliary lesions-", TREMATODES: FASCIOLIASIS
Fasciola hepatica Fascioliasis due to infection with Fasciola hepatica occurs world-wide. US has been found to be useful in diagnosing lesions secondary to infection with this parasite. Although they are relatively large, the individual flukes cannot yet be visualized with ordinary US scanners-",
Tropical Doctor, January 1992
Figure 2. Use of an ophthalmological real-time scanner to visualize a T. solium cyst in the orbit. The scolex of the parasite can be clearly seen (arrowed) (Photo Dr Eduada Moragrega) CESTODES: CYSTICERCOSIS
Cysticercosis is a major parasitic problem in Central America and northern South America (Mexico, Honduras, Peru, Venezuela and Guatemala), China, south and west Africa and non-Islamic southeast Asia including parts of New Guinea. Sporadic outbreaks occur in the USSR and Spain. In Mexico autopsy studies have shown that subcutaneous cysticercosis affects 2-4% of the population; between 70/0 and 10% of all admissions to neurological wards are due to neurocysticercosis. Cysts due to T. solium vary in diameter between 0.5 cm and I em. They are most frequently located in striated muscle, subcutaneous tissues, the brain parenchyma or the eye. US has a limited value in cysticercosis, because the lesions causing the most important clinical problem, neurocysticercosis, are intra-cerebral and therefore cannot be visualized by US. High resolution ophthalmological scanners have been used to identify orbital cysticercosis (Figure 2). Subcutaneous cysts can be detected by simple palpation, and US provides little additional information of clinical value.
17 application of the technique in medicine3 I •32• US revolutionized the diagnosis of intra abdominal hydatidosis, which previously could only be made at laparotomy. (In the abdominal site, cysts cannot be seen on X-ray unless they are calcified.) An accurate diagnosis of CHD can be made if the characteristic daughter cysts or laminated membrane can be visualized'? (Figure 3). With the recent improvements in the sensitivity and specificity of the ELISA test 30 , all proven and suspected cases of CHD should be confirmed serologically. US is useful for monitoring the response of cysts to treatment'! and changes in cyst size and appearance over time36 • Portable US has been particularly useful in several countries (Kenya, Ethiopia, Sudan, Tanzania, Tunisia, Libya, Uruguay and China) where CHD is endemic. The application of US in these settings has shown that the distribution of hydatid disease is often focal. It has highlighted the importance of the disease in many geographical areas and indicated those territories where control measures would be worthwhile". The development of a rapid (20 min) field applicable dot-blot ELISA has facilitated the concurrent collection of US and serological prevalence data. In addition to obtaining prevalence data, US is a valuable technique for monitoring a control programme, as has been done in the Turkana project in Kenya'",
CESTODES: HYDATIDOSIS
Echinococcus granulosus Cystic hydatid disease (CHD) due to infection with Echinococcus granulosus is the most geographically widespread and medically and economically important clinical disorder caused by a cestode. The value of US in the diagnosis of hepatic CHD has been recognized since the earliest days of the
Figure 3. Unilocular CHD due to Echinococcus granulosus with characteristic laminated membrane (arrowed)
Tropical Doctor, January 1992
18
Echinococcus multilocularis The second most frequent form of hydatidosis is alveolar hydatid disease (AHD) caused by E. multilocularis. This cestode is limited to the Holarctic and presents as a chronic disease in humans, who are aberrant hosts (the parasite causes a rapidly developing and fatal disease in its normal wild rodent intermediate hosts). Over 980/0 of all the primary lesions of alveolar hydatid disease are located in the liver, metastases being reported occasionally in the heart, lung and brain. US has been found to compare favourably with CT for diagnosing the condition. The characteristic features on US and CT have been described by a number of authors (reviewed in ref 39). In the majority of cases parasitized liver tissue appears on US as areas of hyperreflectivity without well-defined limits. Lesions are single, multiple or extensive throughout most of the liver. Parasitized areas are heterogeneous and may contain microcalcifications, the presence of which suggest the diagnosis. Early infections may appear as small 'raised' lesions which may be single or multiple; these are relatively simple to detect, but they may be difficult or impossible to differentiate from metastatic malignant deposits. A diagnosis of alveolar hydatid disease should therefore always be confirmed immunologically. Most people (>98%) with active alveolar hydatidosis have diagnostic levels of specific IgG antibody in their plasma. Serological diagnosis is therefore more straightforward than it is for cystic hydatidosis"; Advanced E. multilocularis lesions may produce either a 'hailstorm' or mottled ultrasound picture. There
.~~"" ...,.V"'lu5 ureguuu'
necrotic area
uuraer co me non reflective
irregular non reflective without proper walls (Figure 4). A recent community-based survey in western China demonstrated the feasibility of using US, in conjunction with serology, for mass screening for alveolar hydatid disease in a highly endemic area (Craig, Liu Deshan and Macpherson, in preparation). US changes may also be used for monitoring the effect of chemotherapy, although changes are not as rapid or as clearly visualized as they are in cystic hydatid disease.
Echinococcus vogeli A rare form of hydatidosis is polycystic hydatid disease (PHD) caused by E. vogeli, which is restricted in its geographical distribution to Central and South America. Sonography has been used for the diagnosis of this parasite", which produces large, polycystic fluid-filled cysts primarily in the liver. The sonographical features have not yet been described in detail. NEMATODES: ONCHOCERCIASIS
Onchocerca volvulus infects over 17 million people in a rather patchy distribution throughout Africa, South and Central America and in the Yemen. The adult worms reside in nodules (onchocercomata) which measure between 0.2 em and 8 em in diameter. Nodules usually occur in superficial, subcutaneous sites and can be detected by palpation; a proportion of these may be misidentified and a number of nodules are buried too deep in the tissues to be detected by simple palpation. US has been used for detecting non palpable onchocercomata'-. In the past, instruments had insufficient resolution to allow the internal structural details of nodules to be seen. Recently a number of workers have used high resolution ophthalmological US scanners to demonstrate the characteristic internal features of nodules (homogeneous echogenicity with small echodense particles and a lateral acoustic shadow)43.44. The higher frequency probes used by Leichsenring et 01. 44 can detect nodules in all locations except those obscured by bone or gas, but the screening procedure takes a long time and would not be applicable for screening surveys. Since US can distinguish between worms, fibrosis and necrosis within superficial nodules, it provides a useful method for monitoring the effect of chemotherapy and has been used for monitoring the in vivo effect of a new macrofilaricide, amocarzine" (CGP 6140). US has also been used to visualize lesions due to Ascaris lumbricoides and Toxocara canis but with
Tropical Doctor, January 1992 currently available equipment the technique is unlikely to be of much clinical importance in these infections.
19
14
CONCLUSION
The full potential of US has yet to be realized. With improvements in the resolution, and with reduction in the capital cost of the equipment, it is likely to be a technique that is increasingly utilized, both for individual diagnosis and for community surveys of parasitic disease. REFERENCES
I 2 3 4
5
6
7
8
9
10 11
12
13
Corkill JA, Brabin BJ, Macgregor DF, Alpers MP, Milner ROO. Newborn splenic volumes vary under different malaria endemic conditions. Anch Dis Child 1989;64:541-5 Terrier F, Becker CD, Triller JK. Morphologic aspects of hepatic abscesses at computed tomography and ultrasound. Acta Radiol Diagn (Stockh) 1983;24:129-37 Ahmed L, Salama ZA, EI Rooby A, Strickland GT. Ultrasonic resolution time for amoebic liver abscess. Am J Trop Med Hyg 1989;41:406-10 Macpherson CNL, Kilama WL, Kihamia CM. Miscellaneous parasitic infections. In: Mwaluko GMP, Kilama WL, Mandara MP, Murru M, Macpherson CNL, eds. Health and Disease in Tanzania London: Harper Collins, 1991 World Health Organisation. Proposal for a practical guide to the standardized use of ultrasound in the assessment of pathological changes. 1991. WHO document No.: TDR/SCH/ULTRASON/913 Degremont A, Burnier E, Meudt R, Burki A, Schweizer W, Tanner M. Value of ultrasonography in investigating morbidity due to Schistoma haematobium infection. Lancet 1985;1:662-5 Doehring E, Ehrich JHH, Reider F, Dittrich M, SchmidtEhry G, Brodehl J. Morbidity in urinary schistosomiasis: relation between sonographical lesions and pathological urine findings. Trap Med Parasit 1985;36:145-9 Burki A, Tanner M, Burnier E, Schweizer W, Meudt R, Degremont A. Comparison of ultrasonography, intravenous pyelography and cystoscopy in detection of urinary tract lesions due to Schistosoma haematobium. Acta Trop 1986;43:139-51 Heurtier Y, Lamothe F, Develoux M, et al. Urinary tract lesions due to Schistosoma haematobium infection assessed by ultrasonography in a community based study in Niger. Am J Trop Med Hyg 1986;35:1163-72 Doehring E, Ehrich HH, Bremer HJ. Reversibilityof urinary tract abnormalities due to Schistosoma haematobium infection. Kid Int 1986;30:582-5 King CH, Lombardi G, Lombardi C, et al. Chemotherapybased control of schistosomiasis haematobia. 2. Metrifonate versus praziquantel in control of intensity and prevalence of infection. Am J Trop Med Hyg 1988;39:295-305 Devidas A, Lamothe F, Develoux M, Mouchet F, Sellin B. Ultrasonographic assessment of the regression of bladder and renal lesionsdue to Schistosoma haematobium after treatment with praziquantel. Ann Soc Belg Med Trop 1989;69:57-65 Hatz C, Mayombana C, de Savigny D, et al. Ultrasound scanning for detecting morbidity due to Schistosoma haematobium and its resolution following treatment with
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different doses of praziquantel. Trans R Soc Trop Med Hyg 1990;84:662-5 Laurent C, Lamothe F, Develoux D, Sellin B, Mouchet F. Ultrasonographic assessment of urinary tract lesions due to Schistosoma haematobium in Niger after four consecutive years of treatment with praziquantel. Trop Med Parasitol 1990;41:139-42 Homeida M, Abdel-Gadir A, Cheever A, et al. Diagnosis of pathologically confirmed Symmers' periportal fibrosis by ultrasonography; a prospective blinded study. Am J Trop Med Hyg 1988;38:86-91 Abdel-Waheb MF, Esmat G, Milad M, Abdel-Razek S, Strickland G. Characteristic sonographic patterns of schistosomal hepatic fibrosis. Am J Trop Med Hyg 1989;40:72-6 Homeida M, Ahmed G, DaFalla A, et al. Morbidity associated with Schistosomamansoni infection as determined by ultrasound: a study in Gezira, Sudan. Am J Trop Med Hyg 1988;39:196-201 Doehring-Schwerdtfeger E, Abdel-Rahim 1M, MohamedAli Q, et al. Ultrasonographical investigation of periportal fibrosis in children with Schistosoma mansoni infection: evaluation of morbidity. Am J Trop Med Hyg 1990; 42:581-6 Doehring-Schwerdtfeger E, Mohamed-Ali G, Abdel-Rahim 1M, et al. Sonornorphological abnormalities in Sudanese children with Schistosoma mansoni infection: a proposed staging-system for field diagnosis of periportal fibrosis. Am J Trop Med Hyg 1989;41:63-9 Davidson RN, Houston S, Kiire CF. Schistosomal periportal fibrosis in Zimbabwe: use of ultrasound in patients with oesophageal varices. Trans R Soc Trop Med Hyg 1991; 85:380-2 Homeida MA, DaFalla AA, Kardaman MW, et al. Effect of antischistosomal chemotherapy on the prevalence of Symmers' periportal fibrosis in Sudanese villages. Lancet 1988;11:437-40 Mohamed-Ali Q, Doehring-Schwerdtfeger E, Abdel EIRahim 1M, et al. Ultrasonographical investigation of periportal fibrosis in children with Schistosoma mansoni infection: reversibility of morbidity seven months after treatment with praziquantel. Am J Trop Med Hyg 1991;43:444-51 Murakami H. Image diagnosis of schistosomiasis japonica. Comparison of ultrasonigram with CT image. J Kurume Med Ass 1986;49:458-74 Hirata M, Uno M, Iida H, Uno S, Tsutsumi H, Uto K. Serological evaluation of ultrasound examination for chronic schistosomiasis japonica in a previously endemic area - the Chikugo River Basin, Japan. Ann Trop Med Parasitol 1988;82:475-80 World Health Organisation. Data collection and data analysis in a population with Schistosoma japonicum infection. MPH/WHO document, 1988 Elkins DB, Haswell-Elkins M, Mairiang E, et al. A high frequency of hepatobiliary disease and suspected cholangiocarcinoma associated with heavy Opisthorchis viverrini infection in a small community in north-east Thailand. Trans R Soc Trop Med Hyg 1990;84:715-19 Pungpak S, Sommani S, Sunthara Samai P, Vivatanasesth P. Ultrasonographic study of the biliary system in opisthorchiasis patients after treatment with praziquantel. Southeast Asian J Trop Med Pub Hlth 1989;20: 157-62
20 28 Bronshtein AM, Mironov SP, Silaev AV, Panteleeva EIA. Radionucleotide and sonographic diagnosis of lesions of the hepatobiliary system in opisthorchiasis. Med Parazitol (Mosk) 1989;5:13-17 [in Russian] 29 Chen MG, Mott KE. Progress in assessment of morbidity due to Fasciola hepatica infection: a review of recent literature. Trop Dis BullI99O;87:RI-R38 30 Rogan MT, Craig PS, Zeyhle E, Romig T, Lubano GM, Deshan L. Evaluation of a rapid dot-ELISA as a field test for the diagnosis of cystic hydatid disease. Trans R Soc Trop Hyg 1991;85(in press) 31 King DL. Ultrasonography of echinococcal cysts. J Clin Ultrasound 1973;1:64-7 32 Vicary FR, Cusick G, Shirley 1M, Blackwell RJ. Ultrasound and abdominal hydatid disease. Trans R Soc Trop Med Hyg 1977;71:29-31 33 Macpherson CNL, Romig T, ZeyhleE, Rees PH, Were lBO. Portable ultrasound scanner versus serology in screening for hydatid cysts in a nomadic population. Lancet 1987; 1:259-61 34 Craig PS, Zeyhle E, Romig T. Hydatid disease: research and control in Turkana, 11. The role of immunological techniques for the diagnosis of hydatid disease. Trans R Soc Trop Med Hyg 1986;80:183-92 35 Cossetto B, Gruenewald S, Antico V, Little lH. Albendazole treatment of recurrent hydatid disease: serial evaluation with ultrasound. Aust N Z J Surg 1989;59:933-6 36 Romig T, Zeyhle E, Macpherson CNL, Rees PH, Were lBO. Cyst growth and spontaneous cure in hydatid disease. Lancet 1986;ii:861 37 Macpherson CNL, Spoerry A, Zeyhle E, RomigT, Gorfe M. Pastoralists and hydatid disease: an ultrasound scanning prevalence survey in East Africa. Trans R Soc Trop Med Hyg 1989;84:243-7 38 Macpherson CNL, Wachira T, Zeyhle E, Romig T, Macpherson C. Hydatid disease - Research and control in Turkana, Kenya, IV. The control programme. Trans R Soc Trop Med Hyg 1986;80:196-200 39 Didier D, Weiler S, Rohmer P, et al. Hepatic alveolar echinococcosis: correlative US and CT study. Radiology 1985;154:179-86 40 Gottstein B, Tschudi K, Eckert r, Ammann R. Em2-ELISA for the follow-up of alveolar echinococcus after complete surgical resection of liver lesions. Trans R Soc Trop Med Hyg 1989;83:389-93 41 D'Alessandro A, Rausch RL, Cuello C, Aristizabal N. Echinococcus vogeli in man, with a review of polycystic hydatid disease in Colombia and neighbouring countries. Am J Trop Med Hyg 1979;28:303-17 42 Homeida MA, Mackenzie CD, Williams IF, Ghalib HW. The detection of onchocercal nodules by ultrasound technique. Trans R Soc Trop Med Hyg 1986;80:570-1 43 Poltera AA, Reyna 0, Zea Bores G, Nowellde Arevalo AM, Beltranena F. Detection of skin nodules in onchocerciasis by ultrasound scans. Lancet 1987;1:505 44 Leichsenring M, Troger r, Nelle M, Buttner DW, Darge K, Doehring-Schwerdtfeger E. Ultrasonographical investigations of onchocerciasis in Liberia. Am J Trop Med Hyg 1990;43:380-5 45 Poltera AA, Zea-Flores G, Guderian R, et al. Onchocercidal effects of amocarzine (CGP 6140) in Latin America. Lancet 1991;337:583-4
Tropical Doctor, January 1992
The provision of safe blood - policy issues in the prevention of human immunodeficiency virus transmission C J van Dam MD MSc'* L Fransen MD PhD'
D Sondag-Thull MD PhD 2
'AIDS Task Force, EEC, Brussels and "Service Transfusion Sanguine, Centre Hospitalier Universitaire de Liege TROPICAL DOCTOR,
1992, 22, 20-23
SUMMARY
The AIDS epidemic has focused attention on the constraints and deficiencies present in many blood transfusion services in the developing world. We discuss a variety of options for reducing transfusion-related HIV transmission, and suggest how new transfusion strategies may be implemented. We show that a transfusion service cannot rely solely on the screening of donor blood for anti-HIV antibodies and that a more comprehensive approach is needed. Important components of this approach include donor selection and improved clinical practice, in which blood and blood products are prescribed only when really necessary. INTRODUCTION
The blood borne character of AIDS was detected early in the epidemic, when AIDS in haemophiliacs and children was linked to transfusions of either blood components or bloodt-'. Efforts were made to ensure the safety of transfused blood, although no testing methods were then available. Focus was on the exclusion of donors with the then known high risk behaviours", Today a number of different interventions may contribute to the safety of a blood transfusion service and minimize the contribution of blood transfusion to the transmission of HIV. Options to reduce or prevent transmission of HIV through donor blood fall into four major categories. *Joined since submission the WHO STD Programme, Geneva
