PREY-PREDATOR TRANSMISSION I N THE EP‘IZOOTIOLOGY OF OVINE SARCOSPORIDIOSIS The ubiquitous nature of Sarcocystis spp infections in many host animals is well recognlsed (Levine 1961). It is usual to find microscopic cysts in histological sections of striated muscle from sheep in Australia. Detection of macroscopic muscle cysts in aged animals at the abattoirs leads to condemnation of the tissue and in severe cases to rejection of the carcass. Information on rejection at slaughter collected by officers of the Australian Department of Primary Industries and of the South Australian Department of Agriculture during the last six years has led to recognition of the parasite as a problem in this state. Although the incidence of reported macroscopic cysts in animals from the lowrainfall pastoral zone is at a low level, around 1 % . the level of rejection in some lines of sheep from elsewhere, such as from Kangaroo Island, approaches 100%. Initial histological studies in this laboratory, with naturally infected grazing lambs from a local experimental field station, have shown Sarcosporidia cysts about 10 p in diameter in the muscles by four months of age. Of the three possible modes of infection for sheep - oral (by grazing), parenteral (via biting arthropods), or trans placental (maternal) -the hypothesis of transmission by ingestion was considered as most likely. It was considered probable that Sarcocystis had a similar mode of spread to the other common muscle parasite of sheep, Toenia ovis, that is a dog-sheep cycle, and this was first investigated. In R pilot trial in this laboratory, dogs which were fed macroscopic Surcocystis cysts from the oesophagus of sheep produced a high level of small sporozoan-type cysts in their faeces from 14 days after infection. Control dogs failed to do so. More critical work was then undertaken. Laboratory Beagle bitches at the colony held at this Institute were kept in a manner to preclude sporozoa infection and maintained on pyrimethamine” 50 mg/ 100 kg by mouth twice weekly and sulphaquinoxalinef 0.05% in drinking water for three days weekly to control any possible maternal transmission. All food was processed (heat sterilised). Specific pathogen free (SPF) puppies bred from these bitches were reared under quarantine conditions without drugs. Faeces from the SPF pups were examined at least weekly for several months to ensure there was no contamination or passage of a coccidian-like sporoza infection. The SPE pups were infected with Sarcocystis by feeding fresh meat from Merino lambs containing microscopic muscle cysts. These Iambs had been dosed 5 months previously with the small faecal cysts from other dogs fed muscle cysts in meat in anticipation of the above hypothesis. Faeces from the infected SPF dogs were examined daily between 5 and 50 days after feeding, and otherwise three times each week until they had been negative for two weeks. A qualitative technique sensitive to approximately one cyst in five grams and a modified McMaster counting technique, with saturated magnesium sulphatc as the flotation liquid, were used a t each collection. DOG 0 1 A ....._..__ I 4 a 0 0 10 20 30 40 I 0 60 Figure 2. Sarocystis sporocyst from dog faeces. x W LL 0 ln r ln > u 0 a 0 n ln 0 10 20 30 DAVS SINCE INFECTIVE 40 50 60 FED MEAT Figure 1. The excretion of Sarcocystis sporocysts by dogs fed muscle cysts from sheep. 33 Small cysts were detected in the faeces of the dogs fed meat after 15 days, reaching a peak of the order of 50,000 to 70,000 per gram of faeces around 21 t o 24 days after feeding, as shown for two replicates in Figure 1. After 60 days only low numbers were detected, and no cysts were seen after 90 days. The cysts (Figure 2) were very uniform in size, 15 p long x 10 /I wide. They were considered as coccidian type sporocysts, and contained four spcrozoites and a residual body when excreted. Rarely a pair of cybts surrounded by a thin envelope was detected. There is thus little doubt that Srircocystis sp, at least from the sheep, is a sporozoan parasite with a preypredator transmission. These results confirm a similar relationship found by transmission from sheep t o cats in Germany (Rommel et a1 1972) and in Australia (Durie, 1973, personal communication) However, Rom*“Darapr,im” (Burroughs Wellcome). t“Embaz1n” ( M a y and Baker). Australian Veterinary Journal, Vol. 50, January, 1974 me1 e f a1 (1972) failed to transmit the organism from sheep to dogs, from which it could be implied that it may be normally spread by cats in a similar way to that shown for Toxoplasma (Hutchison et a1 1971). This is unlikely to be of primary importance for Sarcocystis from sheep as the known epizootiological features of the two organisms are different. Further, Dubey (1973) recovered what appeared to be Sarcocysfis sporocysts from only one of 516 cats. He designated these lsospora cati, the larger form of 1. bigemina, as discussed by Wenyon (1926). The close association of working dogs with sheep in Australia. and the potential spread of the small faecal cyst in dust is sufficient to explain the spread of the organism and there is no need to assume an alternative significant source of spread to sheep such as by feral cats, although this must still be assessed. Dogs have ample opportunity to become infected with Sarcocysfis, as with Taenia ovis, due to the management practlces of sheep farmers who feed sheep meat and allow sufficient freedom of dogs to eat from fresh carcasses. If sheep dogs can pass ninety million sporocysts within two months of eating sheep meat as did each dog in this experiment, sheep may be highly exposed to infection when being yarded. Further, our studies of faeces from other dogs submitted for diagnostic examination indicate a continuing excretion of low numbers of Sarcocystis sporocysts from many dogs. Levine and Ivens (1965) also detected similar faecal cysts from four of 139 dogs, but at the time speculated that they may be sporocysts frced from the oocysts of Isospora rivolta. Further studies are in progress to characterise the stages of the Sarcocysfis involved in this prey-predator transmission, and to examine the development in sheep reared Sarcosporidia free. I am grateful for the skill applied by Susanne Bleuler in detecting and counting the sporocysts. Financial support was provided by the Australian Meat Research Committee. G. E. FORD, M.V.Q., Ph.D. Veterinary Pathology Division, Institute of Medical and Veterinary Science, Frome Road, Adelaide, South Australia, 5000. 15 October 1973. References Dubey, J. P. (19731-4. Am. vet. med. Assoc. 162: 873. Hutchison, W. M., Dunachie, J. F., Work, D., and Siim, J. Chr. (1971)--Trans. R. SOC. frop. Med. H y g . 65: 380. Levine, N. D. (1961 )-“Protozoan Parasites of Domestic Animals and of Man”. Burgess; Minneapolis. Levine, N. D. and Ivens, V. (1965)-J. Purasit. 51: 859. Rommel, M., Heydorn, A. 0. and Gruber, F. (1972)Bed. Munch. tierarztl. Wschr. 85: 101. Wenyon, C. M. ( 1926 )-“Protozoology”. Bailliere, Tindall and Cox; London. Whiting, R. H. (1972)-Ausr. vet. J . 48: 449. DETACHED HEADS IN THE EJACULATE OF A HEREFORD BULL The proportion of detached (loose) heads in the ejaculate of normal bulls is less than 1 2 % (Lagerlof 1934; Herman and Swanson 1941; Haq 1949; Blom 1950a; Campbell ef a1 1960). The percentage of detached heads in the ejaculates of a series of 85 normal bulls studied at our laboratory was 5.1 +- 0.74. Increased proportions of detached heads are associated with te‘iticular degeneration and with testicular hypoplasia (Lagerlof 1934; Haq 1949; Blom 1950a, b; Rollinson 1951) and are found in cases of seminal vesiculitis, ampullitis and epididymitis (Blom 1950a; Galloway 1964). A specific condition characterised by a high proportion of detached heads has been described in Guernsey bulls. Cases have been reported in Britain (Hancock and Rollinson 1949; Haq 1949; Hancock 1955) in the island of Guernsey (Alun-Jones 1962) and in South Africa van Rensburg et a1 1966). In the examination of semen the main features were the generally high proportion of detached heads, a high proportion of abnormal tails and low proportion of head abnormalities. Motility was poor to good. Affected bulls were sterile or of very low fertility. Eight Hereford bulls of low fertility with a high proportion of loose heads were described by Williams (1965). Ejaculate volume and concentration were normal. Motility was poor. In four of the bulls there was a high percentage of other abnormal forms. In August 1972 a two year old unmated Hereford bull was examined for routine breeding soundness, which included a detailed study of spermatozoan morphology. The bull was in good health and condition. Physical examination of the reproductive tract revealed no abnormality. The bull had good libido and his serving behaviour was normal. Australian Veteritiary Journal, Vol 50, January, 1974 Semen was collected using an artificial vagina on I 1 August 1972 and 14 August 1972. The bull was run with 30 cows for 10 weeks from September to mid November. Further ejaculates were collected for study on 29 March 1973. Semen was examined as described by Galloway (1965). The results were presented in Table 1. Twenty-eight of the 30 cows became pregnant as judged by rectal examination ten weeks after the completion of mating. The only abnormal feature of the semen examination was the consistently high proportion of detached heads. The cause of this abnormality is not known. The low proportion of other morphological abnormalities indicated there was no testicular degeneration or testicular hypoplasia, and that the condition was dissimilar from that described in Guernsey bulls. In contrast with the semen of the Hereford bulls described by Williams (1965) motility was good. The lack of leucocytes in the semen and the findings at physical examination indicated an absence of inflammatory lesions. The results suggest that fertility in the natural mating situation need not necessarily be impaired by a proportion of detached heads greatly outside normal limits. Caution should be exercised at reproductive soundness examinations in interpreting such findings in otherwise normal animals. The expert technical assistance of Miss Jill Norman in semen assessment is gratefully acknowledged. P. J. WRIGHT, B.V.Sc., M.V.Sc. Department of Veterinary Clinical Studies, University of Melbourne, Werribee, Victoria, 3030. 28 June 1973. 39