Parasites in Small Ruminants and Camelids
—Haemonchus contortus (Barber Pole Worm)
Small ruminants are highly susceptible to internal parasites, primarily gastrointestinal nematodes (worms). The most important of these gastrointestinal parasites is the Barber Pole Worm (Haemonchus contortus) and has become a major problem on a worldwide scale. These parasites are found in the abomasum (“true stomach”) and can cause significant damage and blood loss in your animals, leading to subsequent production losses: poor growth, reduced feed efficiency, anemia, poor milk production, iron and other mineral deficiencies, and even often times death. These issues are intensified if parasite burdens are left unchecked or if dewormers are used in absence of diagnostics (i.e. by using fecal egg counts). Recognizing the prevalence and impact of these parasites is the first step in effective parasite management. This parasite is a hot weather parasite and undergoes a seasonal arrestment (i.e., “hibernation”) during the cold winter months; it invades the abomasum wall and waits until conditions outside the animal are conducive for survival. The Barber Pole Worm produces about 5000 eggs per female worm in a single day, making pasture contamination and reinfection rates very high, especially in situations where animals are not grazed on a large amount of land and/or are confined to small paddocks or lots. In order to create an effective parasite management program in your operation, regardless of how many animals you have, it is vital that you recognize the prevalence of these parasites and impact that they have on your animals.
The Barber Pole Worm is a member of a group of gastrointestinal nematode parasites whose eggs are morphologically indistinguishable (i.e. they look the same and cannot be differentiated) called “Strongyles”. Strongyle parasites are found in all grazing livestock and different parasite species are important depending on the host animal. In small ruminants and camelids, the Barber Pole Worm is the most economically important strongyle parasite, and likely the only parasite that is causing both animal and monetary losses.
However, there are other strongyle parasites that can be commonly found in small ruminants and camelids. These include:
—Trichostrongylus colubriformis (Bankrupt Worm)
The Bankrupt Worm is a nematode that is found in most small ruminants and camelids and rides the coattails of the Barber Pole Worm, so to speak. Though the name elicits an image of a pathogenic worm, the Bankrupt Worm does not take a lot from the host animal and does not produce very many eggs per day (>100/day/female worm). This worm is typically susceptible to most dewormer classes, though it is not recommended to use dewormer to control this worm.
Trichostrongylus colubriformis
—Oesophagostomum venulosum/columbianum (Nodular Worm)
The Nodular Worm is found in the intestinal lining of the end of the small intestine and beginning of the large intestine of ruminants. It invades the intestinal lining as a natural part of the life cycle and can cause significant pathology in animals when found in high numbers. The parasite is typically found in low numbers on roughly 30-50% of operations and generally does not cause a problem. However, due to penetrating the skin as an infection route, if your operation has consistently wet conditions (i.e., heavy and constant rain, dairy operations, etc.), this worm might become an issue. The success of this parasite generally requires a “chronic carrier” host; this is a host animal that will always harbor a heavy infection and persistently seed the pastures with Oesophagostomum eggs.
—Teladorsagia circumcincta (Brown Stomach Worm)
The Brown Stomach Worm of small ruminants is a parasite that is found in the abomasum and is present in the more temperate regions of the world. This parasite can cause issues as it is in the same organ where the Barber Pole Worm resides (where there is geographical overlap), so a concurrent infection with both species could potentially create a more immediate problem. This parasite eats blood and can cause anemia, lesions, poor weight gains, poor milk production, and a poorly functioning organ. It also undergoes a seasonal arrestment (like the Barber Pole Worm), but the seasons are different depending on the geographic region and the intensity of the winter/summer. In the Northern US, the arrestment occurs in the winter and its larvae cycle on pasture during the warmer months. In the Southern US, arrestment occurs during the hotter months of the year and its larvae and persist on pastures during the winter. In the Western US, arrestment season is mixed between the winter and summer. The Brown Stomach Worm has also displayed resistance to Benzimidazoles and Avermectins.
—Chabertia ovina (Large Bowel-Mouthed Worm)
The Large Bowel-Mouthed Worm is a parasite that is found in the more temperate regions of the world, though is typically considered to be of lesser concern when compared to the Barber Pole Worm. It can contribute to economic losses when found in large numbers, such as reduced growth weights. Chabertia displays a seasonal arrestment during the cold winter months where it invades the large intestine lining and has displayed resistance to Benzimidazoles.
—Cooperia curticei (Sheep Cooperiad)
Cooperia curticei can be found in small ruminants but is rather rare in the US and is not typically found in fecal samples. When it is present, the pathology is mild and typically does not cause health problems.