Other Internal Parasites
Other internal parasites that infect small ruminants and camelids that can be important in certain situations (i.e. found in high numbers, immunocompromised animals, etc.) are:
—Eimeria spp. (Coccidiosis)
Coccidiosis is a protozoon parasite that is found in the small intestines and typically causes significant pathology in young and immunocompromised animals. Small to moderate amounts of cocci oocysts can be found in nearly all fecal samples but should only be treated if the infections are extremely high. Generally, coccidiosis is only a problem in birthing or winter barns where young animals are housed on soiled bedding. Coccidiosis is a ‘self-limiting’ disease, meaning if you remove an infected animal from the contaminated environment and get them on a good plane of nutrition, they will clear the infection without treatment in about 7-10 days. If the animal needs to be treated, amprolium or a sulfa drug is sufficient. There are cocci preventatives that can be added to the feed, as well.
—Nematodirus spp. (Intestinal Thread-necked Worm)
The Intestinal Thread-necked Worm is a large worm that is found in the small intestines of ruminants and is found in roughly 10-30% of operations. This parasite can cause significant pathology due to it strangling the intestinal villi, which are very important to the digestion process, as a means to stay in place. This action, called Thigmokinesis, causes the host to reject the villus from the intestinal lining and can cause significant damage. This can lead to weight loss/skinny animals and profuse diarrhea/dehydration. There is no treatment threshold for Nematodirus; if a single egg is seen during a fecal egg count, a Benzimidazole dewormer should be administered. It should be noted that the Benzimidazole dewormer will have no action against an infection of Barber Pole Worms.
Nematodirus Egg
—Trichuris spp. (Ruminant Whipworm)
The Ruminant Whipworm is an internal parasite that is found in the large intestine of ruminants and eats blood. This worm threads 2/3 of its body into the intestinal lining and is very anchored in place, making it difficult to kill with dewormers. The female parasites do not release eggs at a steady interval, instead coordinating the population’s egg output every few days. This coordinated egg dumping makes it difficult to accurately detect if only a single fecal egg count is performed; an egg count must be performed every day for 3-5 days in order to confirm infections. It is typically found in low numbers on roughly 10-25% of operations and generally does not cause significant pathology. The Ruminant Whipworm is typically disregarded and tolerated due to the general failure of dewormers and difficulty to detect via fecal egg counts.
Trichuris Egg
—Strongyloides papillosus (Intestinal Threadworm)
The Intestinal Threadworm is found in the small intestine of ruminants and can be found on the majority of operations and typically does not cause significant pathology. Due to the complexity of its life cycle, its nearly permanent presence in the environment, and the fact that there is no good treatment for it, this parasite is generally disregarded and tolerated.
—Moniezia expansa (Sheep Tapeworm)
The sheep tapeworm is found in the small intestines of small ruminants and is of very little concern. Deworming treatments for tapeworms in ruminants are generally not advised as they do not cause significant pathology and, as such, treatments generally are not required.
—Parelaphostrongylus tenuis (Meningeal/Deer/Brain Worm)
The Meningeal/Deer/Brain Worm is a nematode that is found on the brain of gastropods (except cattle) and can cause significant neurological issues. The natural definitive host is the white-tailed deer; all other hosts are accidental/incidental and experience a plethora of neurological pathology. There are no good treatments for this nematode; anti-inflammatories and steroids are advised in order to reduce swelling of the brain. The infected animals either clear the infection or they don’t, and there is little in-between. This parasite cannot be detected in a fecal egg count and is diagnosed based on necropsy.