Ruminants and horses are infested mainly by the cestodes (tapeworm) belonging to the anoplocephalid family.
Aetiology
Common tapeworms of ruminants (cattle, sheep and goat) are Moniezia expansa, Moniezia benedini, Thysaniezia giardi, Avitellina spp., Stilesia hepatica, Thysanosoma actiniodes.
Common tapeworms of horses are Anoplocephala magna, Anoplocephala perfoliata, Paranoplocephala manillana.
Incidence
M. expansa, M. benedini and T. giardi are cosmopolitan in distribution.
Avitellina spp. ocur in Mediterranean countries and in India.
Stilesia hepatica occurs mainly in Africa. Thysanosoma actinoides occurs in America specially the western part of the United States and also in SOuth America. Anoplocephala magna, A. perfoliata and Paranoplocephala mamillana are cosmopolitan in distribution.
All the tapeworms reside in the small intestine of the animals except Stilesia hepatica and Thysanosoma actiniodes which reside in the bile duct of the affected animals and Anoplocephala perfoliata is found around the ileocaecal junction.
Epidemiology
Infective eggs are taken by the oribatid mites in the pasture. Animals get infected when they accidentally swallow the infected mites while grazing in the pasture. The mature tapeworms develop inside the primary host.
Pathogenesis
Calves, kids and lambs below 6 months of age exhibit changes in the organs. If the tapeworms are present in large number, they may obstruct the lumen of the intestine, distend the wall of the G.I tract causing tympanitis, peritonitis etc. Sometimes, large number of tapeworms may form closely packed ball in the intestine, as a result partial or full obstruction, stasis of the faecal matter and even rupture of the intestinal wall. General intoxication of the tapeworm retards the growth of the animal, lowers down the body resistance and ultimately welcomes the secondary bacterial infection.
In heavy infestation with Thysanosoma actinoides jaundice may be noted.
In Stilesia hepatica infestation, cirrhosis of liver and thickening of bile duct may occur.
In horses, A. perfoliata frequently localises near ileo-caecal valve which may show ulceration, oedema and occassionally a marked excess of granulation tissue. This may lead to partial occlusion of ileocaecal valve. In rare ocassion, acute, massive infection of young horses, an acute catarrhal or ulcerative enteritis may occur. A. magna is probably the most pathogenic of the 3 species, heavy infection of which produces catarrhal or haemorrhagic enteritis.
P. mamillata is seldom responsible for ill health. A recent matched case control study indicated that 22% of a series of spasmodic colic cases and 81% of ileal impaction cases were likely to have been tapeworm associated.
Clinical Findings
Most infestations are asymptomatic but on occasion, heavy burdens may results in unthriftiness, poor coat, vague digestive disturbances including constipation, mild diarrhoea and dysentry and sometimes anaemia. Animals occasionally move in circle and show masticatory movements of jaw.
In horses, loss of appetite, poor growth, unthriftyness, diarrhoea, enlargement of belly are evident. Sometimes they lie down and turn their head back and show increased respiration and pulse rate. Occasionally the symptoms of colic may appear.
Diagnosis
By clinical signs which are not much indicative.
Examination of faecal sample for defaecation of eggs by centrifugation or floatation method using saturated sugar solution.
Examination of faecal sample for detection of shred tapeworm segment.
Methods have been devised for detection of specific antibodies in the serum or antigen in the faeces but are not as yet generally available.
Treatment
For ruminants.
1. Praziquantel @ 3.75 mg/kg is highly effective against Moniezia spp.
For Thysaniezia spp – 5 mg/kg
For Avitellina spp – 7.5 mg/kg
For Stilesia hepatica – 15 mg/kg
2. Some benzimidazole compounds such as albendazole, fenbendazole, mebendazole, oxbendazole have cestocidal activity in ruminants.
Albendazole @ 7.5 mg/kg is effective against cestodes in the bile duct.
For Horses
Pyrantel embonate @ 38 mg/kg is an established treatment for A. perfoliata
Recently Praziquantel @ 1 mg/kg has been evaluated against A. perfoliata and P. mamillana.
Control
Control of the oribatid mites, the intermediate hosts is impractical. Number of the mites can be reduced thorough ploughing of permanent pasture and reseeding. Otherwise stabling or tactical dosing at 6-10 weeks after turn out and in autumn are the only options.
