PARALYSIS OF CALVES BY THE TICK, IXODES HOLOCYCLVS
DOUBE", B.Sc., Ph.D., D. H.
KEMPt,
B.Sc., Ph.D., and P. E. BIRD*
CSIRO, Long Pocket Laboratories, Private Mail Bag No. 3, Indooroopilly, Queensland, 4068 Introduction
Doube and Kemp (1975) showed that British breed calves two to three weeks old were paralysed when challenged with ten females of Ixodes holocyclus, but survived a challenge of two females. Despite these results there remains a strong feeling in the cattle industry and amongst veterinarians (S. R. Knott, personal communication) that one female tick is capable of paralysing a large calf, and it has been suggested that the adult ticks used in the above experiment were of low pathogenicity because they had moulted from nymphs that had fallen from bandicoots and been stored in the laboratory before use. Other suggestions are that the pathogenicity of ticks from different localities or collected in different season could differ, there being evidence for this in Dermacentor andersoni (Gregson 1973), and the site of attachment of the tick on the body could affect its pathogenicity. To examine these possibilities 2-3 week old calves were exposed in various ways to females af I . holocyclus that either had been reared in the laboratory or collected as adults in the field. Materials and Methods Origin and Trcafrn~ntof C U ~ V C S Hereford-Shorthorn calves 2-3 weeks old from Dalby, Queensland, an area where I. holocycl~ts does not occur. were used except for trial 3 in which 2-3 week old Sahiwal x Jersey calves from dairies at Lismore, New South Wales, were included. The Sahiwal x Jersey calves had been raised in concrete yards and 1. Irolncydrts had not been 0hr;erved on the properties in that season so it is unlikely that the calvrs had had previous exposure to I . ~ O ~ O C J ~ (I RL .T Hewettson. personal communication). Calves were weighed on arrival and fed milk and lucerne pellets daily. Aluminium capsiiles with an internal diame'er of 25 mm were glued to the head, rib or rump of the calves. Unfed female ticks were placed in the capsules which were then covered with ga uze . Origin of Ticks In November 1974 unfed adult ticks were collected from the field at Tamborine Mountain, Queensland; Fig Tree Pocket, a siihurb nf Brisbane; and, hv courtesy of Lismore Serum Products, near Lismore N.S.W. Adult males and females were stored toeether at room teni'Division of Entomology. $Division of Animal Health.
Australian Veterinarv Journal, Vol. 5 3 . January, 1977
perature and 95% RH in glass vials and used within 21 days of collection. Ticks were also reared in the laboratory from nymphs which engorged and dropped from bandicoots trapped at Tamborine Mountain during July of 1974 and of 1975. Males and females were maintained together until used. Trials 1 and 2 were carried out in November 1974, and trial 3 in September 1975.
Triul I British breed calves were infested with ticks from Lismore, Fig Tree Pocket (field collected). and Tamborine Mountain (laboratory reared). Two calves received 2 females and 2 calves received 10 females from each group of ticks. All calves were infested on the rib area. T o provide an exact challenge of females more ticks than necessary were applied and the excess ticks were removed the following morning. The time taken for ticks to engorge was noted and engorged ticks were weighed. When calves became paralysed all partially engorged ticks were removed and weighed and the calves were injected intravenously with 10 ml canine anti-tick serum*. Some calves were given further antitick serum. *Limore Serum Products.
Trio1 2 British breed calves were infested on different parts of the body with ticks from Lismore and from Tamborine Mountain (field collected and laboratory reared). Two calves received 2 females and 2 calves received 10 females from Tamborine Mountain (field collected) on the rib area. The infestation schedulc for calves infested on the head and rump is shown in Table 2. Treatment of calves and ticks was similar to that in trial 1 except that the first calf to become paralysed was not treated with serum and the second calf to become paralysed was given 20 ml on paralysis and 20 ml 12 hours later. Trial 3 Britich breed and Sahiwal x Jersey calves were infested with ticks from Tamborine Mountain (laboratory reared). Two calves of each breed received 4 females, and 4 calves of each breed received 10 females. Treatment of calves and ticks was similar to that in trial I except that paralysed calves were not treated with anti-tick serum.
Results and Discussion
In trial 1 (Table 1 ) 10 females paralysed all 6 calves and 2 females whether from the field or the laboratory failed to cause paralysis. In trial 2, ten females paralysed only 1 of the 2 calves used and again 2 females failed to paralyse. Four females also failed to induce paralysis and only 1 of the 4 calves with 8 females 39
TABLE 1 TRIAL 1 . Numhcr of Female I. holocvclus Required to Paralyse 2-3 Week Old Calves Calf No.
1 2 3 4 5
9 10 11
Weight of Calf (kg) 38 33 46 38 40 43 38 34 39 38 39
Origin of Ticks Lismore, Field 1,
Tamborine. Lab. Lismd;e, Fie12 Fig’kree PGcket, Field 7,
10 10 10 10 10
No No No No No No Yes Yes Yes Yes Yes
10
Yes
2 2 2 2 2 2
Fig’kree Pgcket, Field 93
Time to Induce Paralysis ( Days )
No. Attached
9.
Tamborine, Lab.
44 Attachment at 24 hour Origin of Tick Lismore (Field collected) Fig Tree Pocket (Field collected) Tamborine M!. (Laboratory reared)
12
No* Engorged
-
6 8 8 8
2 2 2 2 2 2 5 5 6 9 9
7
9
-
7
0 0 0 0 0 0 5
5 4 1 1 (dead) unfed 1
No. Applied 41 31
% Attached 93 74 80
became paralysed (Table 2). In trial 3 ten females paralysed 7 of 8 calves and 4 females induced paralysis in all 4 cases (Table 3). Trials 1 and 2 were carried out in November using recently collected field ticks or ticks which had moulted from nymphs in the laboratory, where they were kept for 3 to 4 months before use. Clearly a challenge of 8 to 10 such females was sufficient to paralyse young unexposed
No. Partially Engorged
51
calves weighing between 33 to 46 kg and a challenge by a smaller number (for example 4 females) did not induce paralysis (Table 2). In co’ntrast trial 3 showed that a challenge of 4 newly moulted females was sufficient to paralyse similar calves (Table 3). The reason for the greater toxicity of the ticks in trial 3 compared with those in the first two trials is unknown. There were two obvious
TABLE 2 TRIAL 2. Number of Female I. holocyclus Required to Paralyse 2-3 Week Old Calves calf No.
Weight of Caif (kg)
Origin of Ticks
37 Tamborine, Field 2 43 2 IS 41 10 16 38 10 17 41 Lismlre, Fielbt 8 18 46 8 19 42 4 20 42 4 21 41 Tamborine,”Lab. 4 22 40 4 23 43 8 24 42 8 Summary of Trials I and 2 No. of Number of Ticks Area Applied Calves Used per Calf 2 8 rib 4 2 rump 4 2 head 8 2 rump 8 2 head 8 rib 10 13 14
~
40
Time Induce Paralysis (Days)
No. Attached
rumD head
No No Yes No No Yes
rumo
N O
head head rump head rump
No No No No No
rib ,>
,, ,,
7 9 -
No. Engorged
No. partially Engorged
2 2 10 10 8 8 4 4 4 4 8 8
-
0 0 0 0 0 0
0 0 0 0 0 0
Number of Calves
No. Paralysed 0 0 0 0
1 7 ~
~
No. Died 0
No. Survived 8 2 2 2 2 4
0 0 0 0 4 ~~~
Australian Veterinary Journal, Vol. 53, January, 1977
TABLE 3 TRIAL 3. Niiniher of Fcriide 1. holocyclus Reqiiiwd t o Pora1y.w 2-3 Week Old Culve, ~
Weight Calf No.
25 _. 26 27 28 29 30 31 32 33 34 35 36
p:iz)to Infestation
Breed of Calf
34.1 32.i 30.5 27.7 32.7
Hereford-Shorthorn Sahi&l-Jerse; Herehd-&orthorn
3S.O 42.3 40.5 26.4 34.1 33.2 35.0
Sahiwal-Jersey . . . ,..
.,
,,
3,
11
I,
Number of Ticas Attached 4 4 4 4 10 10 10 10 10 10 10 10
No.
Time to Paralysis
Yes Ye5 Yes Yes Yes Yei *No
PInduce a r a l W Engorged No* kngorged (Day>) 11 13 8
9 8 9
-
0
0 0 0 1 0
-
4 4 4 4 9
I0
-
Yes
8
0
10
Yes Yes Yes Yes
8
0 0
10 10 10 10
11 8 8
0
0
Mean Weight of Partially Engorged Tichs
(ms) 45.3 44.0 42.3 39.3 37.1 37.5 38.4 28.5 46.9 32.7 37.2
No. 31 was unsteady i n the hind legs o n the 10th. 1 1 t h and 12th day after infestation.
'Calf
differences. Firstly the ticks in trial 3 were newly moulted whereas the laboratory reared ticks in the first two trials had been stored for 3-4 months before use, and Gregson (1973) has shown that the toxicity of D. andersoni wanes
with storage. Secondly ticks in trial 3 grew slowly and weighed only 30 to 50 mg at the time of paralysis, 8 to 13 days after infestation, whereas most of the ticks in trials 1 and 2 had fully engorged ( > 600 mg) at the time of para-5.0
4.0
80
c.
.-U8 0
70
E
I fn ._ fn
-,m, 6P
3.0
m n
=O
zP
50
z
fn
.-0 s
c.
2.0
40
b
0
2 Q)
b
r
0
z
1.0 p
E a
+ ........ ........ .......
C C
m
r'0
MONTH OF THE YEAR Figure 1. A comparison of the seasonal incidence of female 1. holocyclus on bandicoots from the field i n Southesst Queensland (adapted from Doube [19751) and the incidence of cases
of paralysis i n dogs and cats treated at the Veterinary Clinic of the University of Queensland during the years 1970-75 (data kindly supplied by Mr C. Prescott).
Australion Veterinary Jorirnal, Vol. 53, January, 1977
41
g g sy i-? \OW
39
0
0
.-
6 W
-,o 02
D1
m
I 0 ?
++ l(vN+
0000000
000
-.4-+,+4-
333
+ + +
.-cM
lysis, 6 to 9 days after infestation. Gregson (1973) has shown that “fast feeding” female D. andersoni are less toxic than those which engorge more slowly. It is well known that Ixodid ticks require some time after the moult for complete maturation. For example Zxodes ricinus is not attracted to host stimuli until 2 months after the moult (Lees 1948) and other species will not attach, or if they do so, will only feed slowly unless they are previously matured for some weeks (Balashov 1957). The slow growth of females in trial 3 suggests that they had not fully matured. Hence the differences in toxicity could have been due to the toxicity of the tick changing with season or with age or both, or to variations in the production and injection of the toxin associated with the rate of growth and feeding.
00
The incidence of female I . holocyclus on bandicoots in south eastern Queensland (Doube 1975) and on the vegetation near Lismore, New South Wales (K. Curtin, personal communication) indicates that while females are common from July to December, they are most abundant in October, November and December. However Carter (1972) claimed that most cases of paralysis occurred in late winter and spring (AugustSeptember). The incidence of tick paralysis in dogs and cats in Brisbane (Figure 1 ) and in calves in northern New South Wales (I. J. Lewis, personal communication) also suggests that the highest incidence of paralysis occurs in September, 3 months prior to the peak abundance of female ticks. The explanation of this may be that ticks are more toxic early in the tick season or that animals become increasingly resistant to paralysis as the season progresses, or both. In trials 1 and 2 there was little difference in toxicity between ticks collected from different localities, except that those from Lismore may have been slightly more pathogenic than those from southeast Queensland. The ticks from Lismore induced paralysis about one day earlier than those from Queensland and at the time of paralysis only five had engorged on each of calves No. 7 and 8, and those still attached were relatively small. Ticks from Brisbane and Tamborine Mountain, in contrast, induced paralysis only after most or all of the ticks had engorged and detached (Table 4). In agreement with our earlier results (Doube and Kemp 1975) there were cases (calves No. 11, 15 and 18) where paralysis occurred after all the ticks had engorged and dropped off. Further, the data in Table 2 showed that there was no relationship Australian Veterinary Journal, Vol. 5 3 , January, 1977
between the position of the tick on the host and the ability of the tick to paralyse. In trial 3 previously unexposed calves of both breeds were equally susceptible to tick paralysis (Table 3). Nevertheless there is a belief held by some graziers that Zebu cattle become more resistant to I . holocyclus than do British breed animals. These experiments showed clearly that there was no innate difference between the breeds but it is possible that in the field, Zebu calves are less prone to tick paralysis than British breed calves because they acquire a higher degree of tick resistance. There were no obvious lesions at the feeding site after the ticks had engorged and detached. We have suggested before (Doube and Kemp 1975) that the impression that one female tick will paralyse a calf may arise because paralysis can occur after most of the ticks have dropped off. Calves which become paralysed are commonly those with little or no previous tick experience and so do not form scars at the feeding site. Hence the number of ticks which induce paralvsis in the field cannot be determined unequivocally by examining paralysed calves. Canine anti-tick serum was used in 7 cases and 4 of the calves recovered (Table 4). Three that died received between 10 and 30 ml. All 12 untreated calves died. It is possible that the calves which were treated with serum, and died. might have recovered if given more intensive care. Summary
Adult female Ixodes holocyclus were collected from the field at Fig Tree Pocket, a Brisbane suburb, at Tamborine Mountain, Queensland and at Lismore, New South Wales, in November 1974. Females were also reared from engorged nymphs collected off bandicoots from Tamborine Mountain July 1974 and 1975. In November 1974 unexposed 2-3 week old British breed calves, weighing between 26 and 46 kg were
Accsiraliiin
Veterinary Journal, Vol. 53, January, 1977
infested with 2, 4, 8 or 10 ticks. Neither 2 nor 4 females per calf caused paralysis. A challenge of 8 to 10 females induced paralysis 6 to 9 days after infestation by which time most ticks had engorged. There was little difference between ticks from different geographic localities. The site of attachment had no influence on tick toxicity. In September 1975, 2-3 week old British breed and Sahiwal x Jersey calves were infested with female ticks which had moulted 2-4 weeks prior to infestation. All but one calf with 10 ticks and all calves with 4 ticks became paralysed 8 to 13 days after infestation. At the time of paralysis only 1 of the 86 ticks had engorged and the remainder were small (30 to 50 mg). The greater toxicity of the latter ticks may have been due to the different treatment of ticks prior to infestation or to variations in the production of toxin associated with slow feeding. Four of 7 paralysed calves were saved using canine antitick serum. Acknowledgments
We thank Mr K. Curtin and M. J. Frogley of Lismore Serum Products for their cooperation and for supplying the Lismore ticks and Dr B. F. Stone for supplying the Fig Tree Pocket ticks used in these experiments. Mr R. Hewetson organised the purchase of the Sahiwal x Jersey calves and for this we thank him. References Balashov. Yu. S. ( 1957 - Aidtoref. Dis.~.Soisk. Uchen. Srep. KnnJ. B i d . N a n l : Leningrad. 20pp (CSIRO Translation No. 4506). Doube, B. M. (1975)-Aust. i'd.1. 51: 5 1 1 . Doube, B. M. and Kemp. D. H. (1975)-Airs/. J . ujiric. Res. 26: 635-40. Carrer, G. C. (1972)-Agric. Grrz. N.S.W. 83: 109. Gregson, J. D. (1973)--Monogr. Can. Dep. Agric. No. 9. I e s , A. D. (1948)--3. r x p . B i d . 25: 145. (Rcceit*cdf o r puhlicurion 17 March 1975)
43
DOUBE", B.Sc., Ph.D., D. H.
KEMPt,
B.Sc., Ph.D., and P. E. BIRD*
CSIRO, Long Pocket Laboratories, Private Mail Bag No. 3, Indooroopilly, Queensland, 4068 Introduction
Doube and Kemp (1975) showed that British breed calves two to three weeks old were paralysed when challenged with ten females of Ixodes holocyclus, but survived a challenge of two females. Despite these results there remains a strong feeling in the cattle industry and amongst veterinarians (S. R. Knott, personal communication) that one female tick is capable of paralysing a large calf, and it has been suggested that the adult ticks used in the above experiment were of low pathogenicity because they had moulted from nymphs that had fallen from bandicoots and been stored in the laboratory before use. Other suggestions are that the pathogenicity of ticks from different localities or collected in different season could differ, there being evidence for this in Dermacentor andersoni (Gregson 1973), and the site of attachment of the tick on the body could affect its pathogenicity. To examine these possibilities 2-3 week old calves were exposed in various ways to females af I . holocyclus that either had been reared in the laboratory or collected as adults in the field. Materials and Methods Origin and Trcafrn~ntof C U ~ V C S Hereford-Shorthorn calves 2-3 weeks old from Dalby, Queensland, an area where I. holocycl~ts does not occur. were used except for trial 3 in which 2-3 week old Sahiwal x Jersey calves from dairies at Lismore, New South Wales, were included. The Sahiwal x Jersey calves had been raised in concrete yards and 1. Irolncydrts had not been 0hr;erved on the properties in that season so it is unlikely that the calvrs had had previous exposure to I . ~ O ~ O C J ~ (I RL .T Hewettson. personal communication). Calves were weighed on arrival and fed milk and lucerne pellets daily. Aluminium capsiiles with an internal diame'er of 25 mm were glued to the head, rib or rump of the calves. Unfed female ticks were placed in the capsules which were then covered with ga uze . Origin of Ticks In November 1974 unfed adult ticks were collected from the field at Tamborine Mountain, Queensland; Fig Tree Pocket, a siihurb nf Brisbane; and, hv courtesy of Lismore Serum Products, near Lismore N.S.W. Adult males and females were stored toeether at room teni'Division of Entomology. $Division of Animal Health.
Australian Veterinarv Journal, Vol. 5 3 . January, 1977
perature and 95% RH in glass vials and used within 21 days of collection. Ticks were also reared in the laboratory from nymphs which engorged and dropped from bandicoots trapped at Tamborine Mountain during July of 1974 and of 1975. Males and females were maintained together until used. Trials 1 and 2 were carried out in November 1974, and trial 3 in September 1975.
Triul I British breed calves were infested with ticks from Lismore, Fig Tree Pocket (field collected). and Tamborine Mountain (laboratory reared). Two calves received 2 females and 2 calves received 10 females from each group of ticks. All calves were infested on the rib area. T o provide an exact challenge of females more ticks than necessary were applied and the excess ticks were removed the following morning. The time taken for ticks to engorge was noted and engorged ticks were weighed. When calves became paralysed all partially engorged ticks were removed and weighed and the calves were injected intravenously with 10 ml canine anti-tick serum*. Some calves were given further antitick serum. *Limore Serum Products.
Trio1 2 British breed calves were infested on different parts of the body with ticks from Lismore and from Tamborine Mountain (field collected and laboratory reared). Two calves received 2 females and 2 calves received 10 females from Tamborine Mountain (field collected) on the rib area. The infestation schedulc for calves infested on the head and rump is shown in Table 2. Treatment of calves and ticks was similar to that in trial 1 except that the first calf to become paralysed was not treated with serum and the second calf to become paralysed was given 20 ml on paralysis and 20 ml 12 hours later. Trial 3 Britich breed and Sahiwal x Jersey calves were infested with ticks from Tamborine Mountain (laboratory reared). Two calves of each breed received 4 females, and 4 calves of each breed received 10 females. Treatment of calves and ticks was similar to that in trial I except that paralysed calves were not treated with anti-tick serum.
Results and Discussion
In trial 1 (Table 1 ) 10 females paralysed all 6 calves and 2 females whether from the field or the laboratory failed to cause paralysis. In trial 2, ten females paralysed only 1 of the 2 calves used and again 2 females failed to paralyse. Four females also failed to induce paralysis and only 1 of the 4 calves with 8 females 39
TABLE 1 TRIAL 1 . Numhcr of Female I. holocvclus Required to Paralyse 2-3 Week Old Calves Calf No.
1 2 3 4 5
9 10 11
Weight of Calf (kg) 38 33 46 38 40 43 38 34 39 38 39
Origin of Ticks Lismore, Field 1,
Tamborine. Lab. Lismd;e, Fie12 Fig’kree PGcket, Field 7,
10 10 10 10 10
No No No No No No Yes Yes Yes Yes Yes
10
Yes
2 2 2 2 2 2
Fig’kree Pgcket, Field 93
Time to Induce Paralysis ( Days )
No. Attached
9.
Tamborine, Lab.
44 Attachment at 24 hour Origin of Tick Lismore (Field collected) Fig Tree Pocket (Field collected) Tamborine M!. (Laboratory reared)
12
No* Engorged
-
6 8 8 8
2 2 2 2 2 2 5 5 6 9 9
7
9
-
7
0 0 0 0 0 0 5
5 4 1 1 (dead) unfed 1
No. Applied 41 31
% Attached 93 74 80
became paralysed (Table 2). In trial 3 ten females paralysed 7 of 8 calves and 4 females induced paralysis in all 4 cases (Table 3). Trials 1 and 2 were carried out in November using recently collected field ticks or ticks which had moulted from nymphs in the laboratory, where they were kept for 3 to 4 months before use. Clearly a challenge of 8 to 10 such females was sufficient to paralyse young unexposed
No. Partially Engorged
51
calves weighing between 33 to 46 kg and a challenge by a smaller number (for example 4 females) did not induce paralysis (Table 2). In co’ntrast trial 3 showed that a challenge of 4 newly moulted females was sufficient to paralyse similar calves (Table 3). The reason for the greater toxicity of the ticks in trial 3 compared with those in the first two trials is unknown. There were two obvious
TABLE 2 TRIAL 2. Number of Female I. holocyclus Required to Paralyse 2-3 Week Old Calves calf No.
Weight of Caif (kg)
Origin of Ticks
37 Tamborine, Field 2 43 2 IS 41 10 16 38 10 17 41 Lismlre, Fielbt 8 18 46 8 19 42 4 20 42 4 21 41 Tamborine,”Lab. 4 22 40 4 23 43 8 24 42 8 Summary of Trials I and 2 No. of Number of Ticks Area Applied Calves Used per Calf 2 8 rib 4 2 rump 4 2 head 8 2 rump 8 2 head 8 rib 10 13 14
~
40
Time Induce Paralysis (Days)
No. Attached
rumD head
No No Yes No No Yes
rumo
N O
head head rump head rump
No No No No No
rib ,>
,, ,,
7 9 -
No. Engorged
No. partially Engorged
2 2 10 10 8 8 4 4 4 4 8 8
-
0 0 0 0 0 0
0 0 0 0 0 0
Number of Calves
No. Paralysed 0 0 0 0
1 7 ~
~
No. Died 0
No. Survived 8 2 2 2 2 4
0 0 0 0 4 ~~~
Australian Veterinary Journal, Vol. 53, January, 1977
TABLE 3 TRIAL 3. Niiniher of Fcriide 1. holocyclus Reqiiiwd t o Pora1y.w 2-3 Week Old Culve, ~
Weight Calf No.
25 _. 26 27 28 29 30 31 32 33 34 35 36
p:iz)to Infestation
Breed of Calf
34.1 32.i 30.5 27.7 32.7
Hereford-Shorthorn Sahi&l-Jerse; Herehd-&orthorn
3S.O 42.3 40.5 26.4 34.1 33.2 35.0
Sahiwal-Jersey . . . ,..
.,
,,
3,
11
I,
Number of Ticas Attached 4 4 4 4 10 10 10 10 10 10 10 10
No.
Time to Paralysis
Yes Ye5 Yes Yes Yes Yei *No
PInduce a r a l W Engorged No* kngorged (Day>) 11 13 8
9 8 9
-
0
0 0 0 1 0
-
4 4 4 4 9
I0
-
Yes
8
0
10
Yes Yes Yes Yes
8
0 0
10 10 10 10
11 8 8
0
0
Mean Weight of Partially Engorged Tichs
(ms) 45.3 44.0 42.3 39.3 37.1 37.5 38.4 28.5 46.9 32.7 37.2
No. 31 was unsteady i n the hind legs o n the 10th. 1 1 t h and 12th day after infestation.
'Calf
differences. Firstly the ticks in trial 3 were newly moulted whereas the laboratory reared ticks in the first two trials had been stored for 3-4 months before use, and Gregson (1973) has shown that the toxicity of D. andersoni wanes
with storage. Secondly ticks in trial 3 grew slowly and weighed only 30 to 50 mg at the time of paralysis, 8 to 13 days after infestation, whereas most of the ticks in trials 1 and 2 had fully engorged ( > 600 mg) at the time of para-5.0
4.0
80
c.
.-U8 0
70
E
I fn ._ fn
-,m, 6P
3.0
m n
=O
zP
50
z
fn
.-0 s
c.
2.0
40
b
0
2 Q)
b
r
0
z
1.0 p
E a
+ ........ ........ .......
C C
m
r'0
MONTH OF THE YEAR Figure 1. A comparison of the seasonal incidence of female 1. holocyclus on bandicoots from the field i n Southesst Queensland (adapted from Doube [19751) and the incidence of cases
of paralysis i n dogs and cats treated at the Veterinary Clinic of the University of Queensland during the years 1970-75 (data kindly supplied by Mr C. Prescott).
Australion Veterinary Jorirnal, Vol. 53, January, 1977
41
g g sy i-? \OW
39
0
0
.-
6 W
-,o 02
D1
m
I 0 ?
++ l(vN+
0000000
000
-.4-+,+4-
333
+ + +
.-cM
lysis, 6 to 9 days after infestation. Gregson (1973) has shown that “fast feeding” female D. andersoni are less toxic than those which engorge more slowly. It is well known that Ixodid ticks require some time after the moult for complete maturation. For example Zxodes ricinus is not attracted to host stimuli until 2 months after the moult (Lees 1948) and other species will not attach, or if they do so, will only feed slowly unless they are previously matured for some weeks (Balashov 1957). The slow growth of females in trial 3 suggests that they had not fully matured. Hence the differences in toxicity could have been due to the toxicity of the tick changing with season or with age or both, or to variations in the production and injection of the toxin associated with the rate of growth and feeding.
00
The incidence of female I . holocyclus on bandicoots in south eastern Queensland (Doube 1975) and on the vegetation near Lismore, New South Wales (K. Curtin, personal communication) indicates that while females are common from July to December, they are most abundant in October, November and December. However Carter (1972) claimed that most cases of paralysis occurred in late winter and spring (AugustSeptember). The incidence of tick paralysis in dogs and cats in Brisbane (Figure 1 ) and in calves in northern New South Wales (I. J. Lewis, personal communication) also suggests that the highest incidence of paralysis occurs in September, 3 months prior to the peak abundance of female ticks. The explanation of this may be that ticks are more toxic early in the tick season or that animals become increasingly resistant to paralysis as the season progresses, or both. In trials 1 and 2 there was little difference in toxicity between ticks collected from different localities, except that those from Lismore may have been slightly more pathogenic than those from southeast Queensland. The ticks from Lismore induced paralysis about one day earlier than those from Queensland and at the time of paralysis only five had engorged on each of calves No. 7 and 8, and those still attached were relatively small. Ticks from Brisbane and Tamborine Mountain, in contrast, induced paralysis only after most or all of the ticks had engorged and detached (Table 4). In agreement with our earlier results (Doube and Kemp 1975) there were cases (calves No. 11, 15 and 18) where paralysis occurred after all the ticks had engorged and dropped off. Further, the data in Table 2 showed that there was no relationship Australian Veterinary Journal, Vol. 5 3 , January, 1977
between the position of the tick on the host and the ability of the tick to paralyse. In trial 3 previously unexposed calves of both breeds were equally susceptible to tick paralysis (Table 3). Nevertheless there is a belief held by some graziers that Zebu cattle become more resistant to I . holocyclus than do British breed animals. These experiments showed clearly that there was no innate difference between the breeds but it is possible that in the field, Zebu calves are less prone to tick paralysis than British breed calves because they acquire a higher degree of tick resistance. There were no obvious lesions at the feeding site after the ticks had engorged and detached. We have suggested before (Doube and Kemp 1975) that the impression that one female tick will paralyse a calf may arise because paralysis can occur after most of the ticks have dropped off. Calves which become paralysed are commonly those with little or no previous tick experience and so do not form scars at the feeding site. Hence the number of ticks which induce paralvsis in the field cannot be determined unequivocally by examining paralysed calves. Canine anti-tick serum was used in 7 cases and 4 of the calves recovered (Table 4). Three that died received between 10 and 30 ml. All 12 untreated calves died. It is possible that the calves which were treated with serum, and died. might have recovered if given more intensive care. Summary
Adult female Ixodes holocyclus were collected from the field at Fig Tree Pocket, a Brisbane suburb, at Tamborine Mountain, Queensland and at Lismore, New South Wales, in November 1974. Females were also reared from engorged nymphs collected off bandicoots from Tamborine Mountain July 1974 and 1975. In November 1974 unexposed 2-3 week old British breed calves, weighing between 26 and 46 kg were
Accsiraliiin
Veterinary Journal, Vol. 53, January, 1977
infested with 2, 4, 8 or 10 ticks. Neither 2 nor 4 females per calf caused paralysis. A challenge of 8 to 10 females induced paralysis 6 to 9 days after infestation by which time most ticks had engorged. There was little difference between ticks from different geographic localities. The site of attachment had no influence on tick toxicity. In September 1975, 2-3 week old British breed and Sahiwal x Jersey calves were infested with female ticks which had moulted 2-4 weeks prior to infestation. All but one calf with 10 ticks and all calves with 4 ticks became paralysed 8 to 13 days after infestation. At the time of paralysis only 1 of the 86 ticks had engorged and the remainder were small (30 to 50 mg). The greater toxicity of the latter ticks may have been due to the different treatment of ticks prior to infestation or to variations in the production of toxin associated with slow feeding. Four of 7 paralysed calves were saved using canine antitick serum. Acknowledgments
We thank Mr K. Curtin and M. J. Frogley of Lismore Serum Products for their cooperation and for supplying the Lismore ticks and Dr B. F. Stone for supplying the Fig Tree Pocket ticks used in these experiments. Mr R. Hewetson organised the purchase of the Sahiwal x Jersey calves and for this we thank him. References Balashov. Yu. S. ( 1957 - Aidtoref. Dis.~.Soisk. Uchen. Srep. KnnJ. B i d . N a n l : Leningrad. 20pp (CSIRO Translation No. 4506). Doube, B. M. (1975)-Aust. i'd.1. 51: 5 1 1 . Doube, B. M. and Kemp. D. H. (1975)-Airs/. J . ujiric. Res. 26: 635-40. Carrer, G. C. (1972)-Agric. Grrz. N.S.W. 83: 109. Gregson, J. D. (1973)--Monogr. Can. Dep. Agric. No. 9. I e s , A. D. (1948)--3. r x p . B i d . 25: 145. (Rcceit*cdf o r puhlicurion 17 March 1975)
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