Tapeworms often cause more worry among sheep and goat producers than stomach worms (nematodes), because producers can see the obviously expelled worms, whereas they cannot see stomach worms, only their symptoms.
Tapeworms are flat, ribbon-shaped worms that live inside the intestines of humans or animals that have a spine. They are long, segmented worms of the class Cestoda, which comprise one of three classes of parasitic worms. The other classes are Nematoda (roundworms) and Trematoda (flukes). Cestodes lack an intestinal tract, but are able to absorb nutrients through their skin.
Adult tapeworms have hooks, spiny structures, or suckers on their head, which allow them to attach to the wall of the intestine. The rest of the tapeworm is made up of a chain of flat segments.
The adult tapeworm consists of a head (scolex), where the worms attaches itself to the mucosa of the intestine; a neck; and a segmented body that contains both male gonads and female gonads (proglottids). Mature tapeworms shed segments, which are expelled with the feces. These segments are packed with eggs.
Cestodes (tapeworms) require an intermediate host to complete their life cycle. Different tapeworms require different intermediate hosts. All of the important species affecting sheep, goats, and cattle require pasture mites. These mites ingest the eggs while feeding and the larval stages of the worm develop inside the mites.
Oribatid mites live in the top layer of soil. Sometimes they can be found in plant material. These mites live in huge numbers. Hundreds of thousands can live in one square meter of soil. To see one well, you would need a microscope. Sheep and goats become infected when they ingest the mites containing tapeworm larvae. Once inside the animal, it takes 6 to 7 weeks for the larvae to develop into adult tapeworms.
Moniezia expansa is the tapeworm that commonly affects sheep and goats. Moniezia benedeni, more common in cattle, can also be found in sheep and goats. Sheep and goats serve as intermediate hosts for several other species of tapeworms.
Tapeworm segments can be seen in the feces of sheep and goats. They have a white, grain-like appearance. Adult worms, often up to a meter or more in length, can be expelled and passed in the environment.
Tapeworm eggs can be seen in sheep and goat feces, using the standard worm count procedure. Eggs are triangular in shape.
Definitive diagnosis in the live animal is difficult and sometimes a post-mortem is necessary to confirm an accurate diagnosis. Tapeworm infection is more typically diagnosed when the moving segments are seen crawling around the anus or in a bowel movement. While tapeworm eggs can be seen in fecal flotation under a microscope, fecal analyis does not offer a definitive diagnosis. The symptoms of extreme tapeworm infection are similar to the symptoms of other roundworm infection: diarrhea, emaciation, pot belly, and weight loss. In sufficient numbers, tapeworms can obstruct the bowel and cause death. Sheep seem to develop an immunity to tapeworms relatively early in life (3-4 months of age).
Treatment and control
Four drugs are typically used to treat tapeworm infections in animals: praziquantel, albendazole (Valbazen®), oxyfendazole (Synathic®), and fenbendazole (SafeGuard®, Panacur®). In the United States, praziquantel is marketed for dogs and cats under the tradenames Droncit® and Drontal®. Praziquantel is an ingredient in several horse dewormers: Zimecterin® Gold Paste, Equimax™ Paste, and Quest® Plus Gel. Many anthelmintics marketed in other countries (for sheep and goats ) have a praziquantel component. There are no anthelmintics which contain praziquantel that are currently labeled for sheep and goats in the U.S.
Praziquantel is effective against both the adult and immature stages of tapeworms whereas the benzimidazole anthelmintics only kill the head and segments. Albendazole is considered to be the most effective of the benzimidazole drugs. While it usually less effective than praziquantel, it is usually sufficient for controlling tapeworm infections. Fenbendazole is not labeled for the control of tapeworms (in goats), but will aid in their removal (heads and segments), if the dose is doubled. Oxfendazole is not label for use in either sheep or goats in the U.S.
There are several old remedies with purported activity against adult tapeworms. These include pumpkinseeds, powdered areca (fruits of betel palm, Areca catechu), kousso (flowers of an Abyssinian tree, Hagenia abyssinica), turpentine (oily mixture of exsudates from coniferous trees, especially longleaf pine), pomegranate root bark (tropical Asian and African tree, Punica granatum), and male fern (Dryopteris filix-mas). For a long time, lead arsenate (often mixed with phenothiazine) was used to control tapeworm infections in lambs. It’s safety margin is low; thus, it is no longer used.
Reviews of research show that tapeworms do not cause any ill effects on sheep or lambs despite their rather troublesome appearance. If sheep or lambs are looking poorly and tape segments are in the dung, you should probably look for causes other than tapeworms. The true cause of ill thrift is probably nutritional or other non-visible worms such as Haemonchus contortus (barber pole worm).
Author: by SUSAN SCHOENIAN