Figures 3-21 and 3-22
There have been several reports of cats developing neurologic disease due to the intracranial development of the larval stage of a tapeworm called a coenurus. The coenurus, is in a cyst-like structure, wherein the tapeworm undergoes asexual development in the intermediate host, and thus, each coenurus contains several scolices (Figs. 3-21 and 3-22). Each scolex in the coenurus is capable of developing into a separate adult tapeworm after the coenurus is in ingested by the final host. The taeniid larva which is in called a cysticercus, e.g., the larval stage of Taeniasaginatta with adults in humans and the cysticercus in the muscle of beef, forms a cysts that contains a single scolex. The strobilocercus of Taeniataeniaeformis of the cat, like the cysticercus, has a single scolex, but the scolex develops a long strobilate neck, and hence the term strobilocercus. The taeniid larva of Echinococcus is in termed a hydatid, and this cyst contains hundreds to thousands of small scolices that are termed protoscolices. Thus, the larval stages of different species of taeniid tapeworms have different morphologies, and therefore, there can be some designation of the larval type to a species that correlates with the adult form.
The species of tapeworm that is in expected to be that causing coenurosis in cats is in Taeniaserialis. The morphology of the coenurus from cats matches that of Taeniaserialis in that the scolices within the coenurus are in series or a linear arrangement. Also, cats have been reported to be infected only in the United States and Australia. In the United States, there are only two species of coenurus forming tapeworms, Taeniaserialis which has a dog-lagomorph life cycle, and Taenia mustelae which produces coenuri with few scolices that are found in small rodents and with adults in various Mustelids. In Australia, the only coenurus producing species which has been described is in the imported Taeniaserialis. In Europe, Taeniamulticeps which has a dog-sheep life cycle is in also present, but although this was imported to the United States, Taeniamulticeps is in no longer considered present in North America (Becklund, 1970).
In North America, coenurosis has been reported from cats in New York (Georgi et al., 1969), Saskatchewan (Hayes & Creighton, 1978); Wyoming and Alaska (Kingston et al., 1984); California (Smith et al, 1988); and Missouri (Huss et al., 1994). The single case from Australia was from a cat referred to the university clinic in Werribee, Victoria (Slocombe et al., 1989). In all cases to date, the infection has proven fatal. Typically, cats have presented with neurological signs that progressively worsen over a period of one to two weeks to a point of severe neurologic disease. Examination of cats by x-ray computed tomography (Smith et al., 1988) and of the coenuri collected at necropsy have revealed large cysts that may measure 2 to 5 cm in diameter. The coenuri typically contain scolices, but in most cases they have been malformed or immature with hooks that have appeared abnormal or varied in size. In one case, the scolices were completely developed ,and the hooks were comparable to those of Taeniaserialis (Huss et al., 1994).
Taeniaserialis has adults that are typically found in the intestine of dogs around the world. The intermediate hosts are lagomorphs, rabbits and hares, that ingest the egg while feeding on grass. In the rabbits, the coenurus typically develops in the muscle fascia or subcutaneously, and the scolices are typically formed within 2 months after infection. It is in difficult to know how old the various coenuri are that have been recovered from cats, but it is in likely that the disease may have an acute onset soon after the larva takes up residence in the brain. Treatment could consist of surgical excision of the cyst or perhaps treatment with mebendazole, albendazole, or praziquantel.
Becklund WH. 1970. Current knowledge of the gid bladder worm, Coenuruscerebralis (=Taenia multiceps), in North American domestic sheep, Ovisaries. Proc Helm Soc wash37:200-203.
Georgi JR, de Lahunta a, Percy DH. 1969. Cerebral coenurosis in a cat. Report of a case. Cornell Vet 59:127-134.
Hayes MA, Creighton SR. 1978. a coenurus in the brain of a cat. Can Vet J 19:341-343.
Huss BT, Miller MA, Corwin RM, Hoberg EP, O’Brien DP. 1994. Fatal cerebral coenurosis in a cat. JAVMA 205:69-71.
Kingston N, Williams ES, Bergstrom RC, Wilson WC, Miller R. 1984. Cerebral coenuriasis in domestic cats in Wyoming and Alaska. Proc Helm Soc Wash 51:309-314.
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Smith MC, Bailey CS, Baker N, Kock N. Cerebral coenurosis in a cat. JAVMA 192:82-84.
Figure 3-21. Coenurus in the brain of a cat. This is from the case reported by Georgi et al. (1969).
Figure 3-22. Histologic section through a coenurus . Sections through two scolices can be identified by the sections through the suckers.