THE ISOLATION OF A ROSS RIVER VIRUS FROM A HORSE During 1977 foaling season, a group of 5 Arabian mares foaled between August and December. Four of the foals developed one or more contracted tendons from 4-6 weeks post-partum. Forced extension by means of acrylic wedges corrected the condition over a period of several months in 3 of the foals, the fourth still exhibits a deformity shown as a contracted hoof with a very straight wall. The possiblity of an arbovirus being implicated was considered. Blood samples were collected from 4 of the mares and their affected foals on 27 April and from 3 of the mares and their foals again on 12 June 1978. A cytopathogenic agent was isolated from the blood collected on 27 April from one of the mares in baby hamster kidney (BHK2I) tissue cultures by the method described by St George er al(1977). The agent was able to pass a 220 nm membrane filter* without loss of titre, but its titre was reduced by, passage through a 100 nm filter. The agent killed or paralysed one-day-old suckling mice 4 days after the intracranial injection of tissue culture fluid containing it. This interval reduced to 3 days after 3 further passages. After the intraperitoneal injection of the agent, suckling mice were paralysed in 5 days. A haemagglutinin prepared from mouse blood infected by the agent by the method of Clarke and Casals (1958). and modified by Doherty era/(1971), agglutinated gander erythrocytes at a pH of 6.2. The agent was identified as a strain of Ross River virus in a microtitre test using Vero cells. The serological method was essentially that described for Akabane virus by Cybinski e t a / (1978), with the substitution of the T48 strain of Ross River virus (Doherty et a / 1963) and an antiserum to it produced in a rabbit for the corresponding akabane virus reagents. The healthy 8-year-old mare, from which the Ross River virus was isolated, did not have any neurtralising antibodies in its serum to either the homologous or the T48 strains of virus on 27 April 1978. However, seruni collected from the same mare on I2 June 1978 had neutralising antibodies with titres of ‘Millipore C‘orporalion. United Slates 01 America
64 and 24, respectively, t o both virus strains. One of the other 2 mares bled on both dates had a static titre (approximately 8) and the other was negative. None of the foals had antibodies to either strain of Ross River virus. The evidence indicates that infection of an adult horse with Ross River virus was subclinical in this instance, and that the condition of contracted tendons in the Arabian foals was not related to infection with Ross River virus. Ross River virus was established as a cause of polyarthritis in man by Doherty et a / (I97 I ) . Card e f a1 (1977) have suggested that Ross River virus was associated with muscle stiffness and joint swelling in a horse on the basis of reduction of a high titre of antibody by treatment of the serum with 2 mercaptoethanol, which is a method for indicating recent infection. However, Ross River virus has not yet been established as a cause of disease in horses. We wish to acknowledge the technical assistance of Miss P. M . Williams and Miss S. M. Moore. R. R . R. PASCOE, Oakey, Queensland 4401 T . D. ST GEORGE, D. H . CYBINSKI, CSIRO, Division of Animal Health, Private Bag No. 3 , P . O . Indooroopilly, Queensland 4068 I0 October 1970
References Clarke, D. H. and Casals, J. (1958) - Am. J . frop. Med. H-vg., 7: 561. Cybinski, D. H., St George, T. D. and N. I . Paul1 (1978) Aust. vet. .I. 54: I . Doherty, R. L., Whitehead, R. H., Gorman. G . M. and O’Cower, A. K . (1963) - Aust. J . Sci. 26: 183. Doherty, R. L., Barrett, E. J . , Gorman, B. M . and Whitehead, R . H. (1971) - Med. J . Ausr. 1: 5. Card, G. P., Marshall, I.D., Walker, K . H., Acland, H. M. and De Sarem, W . G. ( 1977) - Ausf. v e t J . 53: 61.
PARASITIC ARTERlTlS AND ITS CONSEQUENCES IN HORSES The communication of Dixon and Brownlow (1978) describes an important sequel to parasitic arteritis in a young foal. Some indication of the prevalence of thromboembolic infarction of the intestine and other related intestinal diseases that occur as a result of parasitic arteritis is available in the records of this veterinary clinic. Of 417 horses referred to this clinic with severe colic o r related intestinal disorders between I July 1970 and I July 1978, 39 (9.53%) have been associated directly with the effects of parasitic arteritis. The majority of these have been cases of thromboembolic infarction of the large bowel with peritonitis, rupture or abscessation. The prevalence in thoroughbreds and standardbreds (8.5% and 7.5% respectively) was lower than that in ponies and other breeds (13.1% and 11.7%) and possibly reflects the better attention to parasite control in the former breeds. Prevalence expressed as a percentage of total admissions for enteric disorders according to age is shown in Table I.Parasitic arteritis was directly related to enteric disorders in all age groups, but the prevalence was especially high in admissions aged between 6 months and 2 years. Three foals under 6
600
months of age were affected. The youngest was 15 weeks of age and died suddenly with rupture of the colon following thromboembolic infarction. There was no significant seasonal variation in occurrence. A seasonal variation in arterial worm population has been TABLE 1
Age Prevalence in Horses of Enteric Disorders Resulting from Parasitic Vasculitis Given as Percentage of Total Admissions for Enteric Disorders in Each Age Group Age
0 - 6 months 6 - 12 months Yearling 2 - 4 years 5 - 9 years 10 - 14 years 15 years and older
Prevalence (%)
4.3 33.0 15.0 7.8 9.4 9.4 10.0
Australian Veterinary Journal. Vol. 54, December, 1978
described for Strongylus vulgaris (Ogbourne and Duncan 1977). These figures arc derived only from cases where the diagnosis was made following surgical exploration of the abdomen and/or pathological examination of removed tissues or the carcase, and where the lesions were directly attributable to parasitic vasculitis. Cases diagnosed on clinical grounds and other forms of colic less obviously attributable to parasitic vasculitis have not been included. For these reasons the figures are undoubtedly a conservative estimate of the importance of parasitic vasculitis in inducing severe enteric disorders in the horse. C. C. GAY, \’. C. SPEIKS,
University of Melbourne, Veterinary Clinical Centre, Princes Highway, Werribee, Victoria, 3030. 23 October 1978
References Dixon, R. J . and Brownlow, M. A. (1978) - Aost. vet. J . 54: 494. Ogbourne, C. D. and Duncan, J . L. (1977) - Strongylus vulgaris in the horse: i t s biology a n d veterinary importance, Commonwealth Agricultural Bureaux. Farnham Royal, England.
ULCERATION OF THE PARS OESOPHAGIA IN PIGS Numerous abattoir surveys and experiments have been conducted to determine the incidence and causes of ulceration of the pars oesophagia of pigs (O’Brien 1969). However, few attempts have been made to assess their importance in pig production. In South Australia, field outbreaks in which severe ulceration with gastric haeniorrhage and death has been observed, have been recorded on less than 10 occasions during the last 15 years. In the majority of cases grower pigs were affected. The aetiology of gastric ulceration is not fully understood. The type and fineness of the grain used and the process of pelleting feeds are considered important. Finely ground maize and wheat based rations pelleted under temperatures which gelatinise starch crystals appear to be more likely to cause ulcers than coarsely ground barley diets fed unpelleted (Mahan el a/ 1966; Nuwer el a / 1967; O’Brien 1969; Bjorkland et a/ 1970; Sabac and Schroeder 1970). Two experiments were carried out in pigs to examine aspects of gastric ulceration using diets containing wheat as the predominant grain component. The purpose was to investigate the role of grain particle size and the pelleting procets in causing ulcers. I n addition, information was sought on (he effect of gastric ulcers on growth rate and feed conversion efficiency.
In each of the experiments, 64 piglets were derived from 16 litters of a batch farrowing of Minimal Disease pigs from the Northfield Pig Research Unit. These were stratified in terms of weight, age, sex and genetic background and divided into 16 groups. One pig from each group was then randomly assigned to one of the 4 treatments in each experiment. Pigs were individually fed twice daily from 20 to 75 kg liveweight. The quantity offered was calculated from a regression curve based on feeding 5% of the animals liveweight at 20 kg. 4% at 45 kg and 2.0% a t 70 kg. Quantity of feed was adjusted weekly. Daily feed consumption was recorded. The composition of the diets was wheat 80%, meat meal (50% protein) 12O70, fish meal 5 % , lucerne 2.5%, salt 0.25% together with minerals and vitamins normally added to conventional pig diets. The first experiment compared the effect of both finely ground and coarsely ground wheat diets when pelleted using either a comniercial steam pelleting process or a cold water and pressure process. The second experiment compared 3 finely ground wheat rations; 2 were pelleted as above and a third was fed unpelleted. A cold pelleted barley based diet was used as a control. The latter was the standard diet used at the Unit.
TABLE 1
Degree of’Gaslric Ulceration in Pigs Fed Pelleted Diets Made From Finely and Coarsely Ground Grains Progress ot Ulceration
Diet Fine Wheat Hot Pellet
Fine Wheat Cold Pellet
Coarse Wheat Hot Pellet
Coarse Wheat Cold Pellet
13/16 1/16 0116
10116 5/16 1/16
Experiment I . Keratinisation only Keratinisation plus erosions Keratinisation plus ulceration
12/16* 1/16 0116
7/16 2/16 7/16
Fine Wheat Hot Pellet
Fine Wheat Cold Pellet
1112 +++ 12/12 ++ 1 1112 ++
1/12+++ 11/12++ 10/12++
Fine Wheat Unpelleted
Control barley Cold Pellet
Experiment 2. Keratinisation only Keratinisation plus erosioiis Keratinisation plus ulceration
+ *
9/12 + 211 2 ++ 1/12 +
3/12 ++ 7112 + 2/12 +
Minimal ++ Moderate +++ Extensive N u m b e r o f pigs affected o u t of total number of pigs.
Austra/ian Veterinary Journal, Vol. 54, Decembcr, I978
60 1
64 and 24, respectively, t o both virus strains. One of the other 2 mares bled on both dates had a static titre (approximately 8) and the other was negative. None of the foals had antibodies to either strain of Ross River virus. The evidence indicates that infection of an adult horse with Ross River virus was subclinical in this instance, and that the condition of contracted tendons in the Arabian foals was not related to infection with Ross River virus. Ross River virus was established as a cause of polyarthritis in man by Doherty et a / (I97 I ) . Card e f a1 (1977) have suggested that Ross River virus was associated with muscle stiffness and joint swelling in a horse on the basis of reduction of a high titre of antibody by treatment of the serum with 2 mercaptoethanol, which is a method for indicating recent infection. However, Ross River virus has not yet been established as a cause of disease in horses. We wish to acknowledge the technical assistance of Miss P. M . Williams and Miss S. M. Moore. R. R . R. PASCOE, Oakey, Queensland 4401 T . D. ST GEORGE, D. H . CYBINSKI, CSIRO, Division of Animal Health, Private Bag No. 3 , P . O . Indooroopilly, Queensland 4068 I0 October 1970
References Clarke, D. H. and Casals, J. (1958) - Am. J . frop. Med. H-vg., 7: 561. Cybinski, D. H., St George, T. D. and N. I . Paul1 (1978) Aust. vet. .I. 54: I . Doherty, R. L., Whitehead, R. H., Gorman. G . M. and O’Cower, A. K . (1963) - Aust. J . Sci. 26: 183. Doherty, R. L., Barrett, E. J . , Gorman, B. M . and Whitehead, R . H. (1971) - Med. J . Ausr. 1: 5. Card, G. P., Marshall, I.D., Walker, K . H., Acland, H. M. and De Sarem, W . G. ( 1977) - Ausf. v e t J . 53: 61.
PARASITIC ARTERlTlS AND ITS CONSEQUENCES IN HORSES The communication of Dixon and Brownlow (1978) describes an important sequel to parasitic arteritis in a young foal. Some indication of the prevalence of thromboembolic infarction of the intestine and other related intestinal diseases that occur as a result of parasitic arteritis is available in the records of this veterinary clinic. Of 417 horses referred to this clinic with severe colic o r related intestinal disorders between I July 1970 and I July 1978, 39 (9.53%) have been associated directly with the effects of parasitic arteritis. The majority of these have been cases of thromboembolic infarction of the large bowel with peritonitis, rupture or abscessation. The prevalence in thoroughbreds and standardbreds (8.5% and 7.5% respectively) was lower than that in ponies and other breeds (13.1% and 11.7%) and possibly reflects the better attention to parasite control in the former breeds. Prevalence expressed as a percentage of total admissions for enteric disorders according to age is shown in Table I.Parasitic arteritis was directly related to enteric disorders in all age groups, but the prevalence was especially high in admissions aged between 6 months and 2 years. Three foals under 6
600
months of age were affected. The youngest was 15 weeks of age and died suddenly with rupture of the colon following thromboembolic infarction. There was no significant seasonal variation in occurrence. A seasonal variation in arterial worm population has been TABLE 1
Age Prevalence in Horses of Enteric Disorders Resulting from Parasitic Vasculitis Given as Percentage of Total Admissions for Enteric Disorders in Each Age Group Age
0 - 6 months 6 - 12 months Yearling 2 - 4 years 5 - 9 years 10 - 14 years 15 years and older
Prevalence (%)
4.3 33.0 15.0 7.8 9.4 9.4 10.0
Australian Veterinary Journal. Vol. 54, December, 1978
described for Strongylus vulgaris (Ogbourne and Duncan 1977). These figures arc derived only from cases where the diagnosis was made following surgical exploration of the abdomen and/or pathological examination of removed tissues or the carcase, and where the lesions were directly attributable to parasitic vasculitis. Cases diagnosed on clinical grounds and other forms of colic less obviously attributable to parasitic vasculitis have not been included. For these reasons the figures are undoubtedly a conservative estimate of the importance of parasitic vasculitis in inducing severe enteric disorders in the horse. C. C. GAY, \’. C. SPEIKS,
University of Melbourne, Veterinary Clinical Centre, Princes Highway, Werribee, Victoria, 3030. 23 October 1978
References Dixon, R. J . and Brownlow, M. A. (1978) - Aost. vet. J . 54: 494. Ogbourne, C. D. and Duncan, J . L. (1977) - Strongylus vulgaris in the horse: i t s biology a n d veterinary importance, Commonwealth Agricultural Bureaux. Farnham Royal, England.
ULCERATION OF THE PARS OESOPHAGIA IN PIGS Numerous abattoir surveys and experiments have been conducted to determine the incidence and causes of ulceration of the pars oesophagia of pigs (O’Brien 1969). However, few attempts have been made to assess their importance in pig production. In South Australia, field outbreaks in which severe ulceration with gastric haeniorrhage and death has been observed, have been recorded on less than 10 occasions during the last 15 years. In the majority of cases grower pigs were affected. The aetiology of gastric ulceration is not fully understood. The type and fineness of the grain used and the process of pelleting feeds are considered important. Finely ground maize and wheat based rations pelleted under temperatures which gelatinise starch crystals appear to be more likely to cause ulcers than coarsely ground barley diets fed unpelleted (Mahan el a/ 1966; Nuwer el a / 1967; O’Brien 1969; Bjorkland et a/ 1970; Sabac and Schroeder 1970). Two experiments were carried out in pigs to examine aspects of gastric ulceration using diets containing wheat as the predominant grain component. The purpose was to investigate the role of grain particle size and the pelleting procets in causing ulcers. I n addition, information was sought on (he effect of gastric ulcers on growth rate and feed conversion efficiency.
In each of the experiments, 64 piglets were derived from 16 litters of a batch farrowing of Minimal Disease pigs from the Northfield Pig Research Unit. These were stratified in terms of weight, age, sex and genetic background and divided into 16 groups. One pig from each group was then randomly assigned to one of the 4 treatments in each experiment. Pigs were individually fed twice daily from 20 to 75 kg liveweight. The quantity offered was calculated from a regression curve based on feeding 5% of the animals liveweight at 20 kg. 4% at 45 kg and 2.0% a t 70 kg. Quantity of feed was adjusted weekly. Daily feed consumption was recorded. The composition of the diets was wheat 80%, meat meal (50% protein) 12O70, fish meal 5 % , lucerne 2.5%, salt 0.25% together with minerals and vitamins normally added to conventional pig diets. The first experiment compared the effect of both finely ground and coarsely ground wheat diets when pelleted using either a comniercial steam pelleting process or a cold water and pressure process. The second experiment compared 3 finely ground wheat rations; 2 were pelleted as above and a third was fed unpelleted. A cold pelleted barley based diet was used as a control. The latter was the standard diet used at the Unit.
TABLE 1
Degree of’Gaslric Ulceration in Pigs Fed Pelleted Diets Made From Finely and Coarsely Ground Grains Progress ot Ulceration
Diet Fine Wheat Hot Pellet
Fine Wheat Cold Pellet
Coarse Wheat Hot Pellet
Coarse Wheat Cold Pellet
13/16 1/16 0116
10116 5/16 1/16
Experiment I . Keratinisation only Keratinisation plus erosions Keratinisation plus ulceration
12/16* 1/16 0116
7/16 2/16 7/16
Fine Wheat Hot Pellet
Fine Wheat Cold Pellet
1112 +++ 12/12 ++ 1 1112 ++
1/12+++ 11/12++ 10/12++
Fine Wheat Unpelleted
Control barley Cold Pellet
Experiment 2. Keratinisation only Keratinisation plus erosioiis Keratinisation plus ulceration
+ *
9/12 + 211 2 ++ 1/12 +
3/12 ++ 7112 + 2/12 +
Minimal ++ Moderate +++ Extensive N u m b e r o f pigs affected o u t of total number of pigs.
Austra/ian Veterinary Journal, Vol. 54, Decembcr, I978
60 1
