Check Your Sheep and Goats: Barber Pole Worms Thrive During Humid Summers

FAMACHA scoring of sheep is used to control parasitic barber's pole worm.

With summer knocking on the door, the inevitable battle with internal parasites is underway.

Unfortunately for sheep and goat producers, this is a perennial problem that has become difficult to control in this part of the country.

The greatest production challenge facing small ruminant producers worldwide is internal parasite infection resulting in loss of production.

Global concern for parasitism in small ruminants focuses primarily on gastrointestinal nematodes, of which the barber pole worm (Haemonchus contortus) is the one of greatest concern.

Production losses resulting from barber pole worm infection include reduced weight gain, decreased wool production, and death due to anemia. Death loss accounts for millions of dollars to producers annually.

This problem is amplified by anthelmintic resistance in worm populations. Loss of effective treatment and limited hope for new drug development means increased deaths and has producers scrambling for alternatives.

To combat anthelmintic resistance, producers have adopted more labor-intensive control methods to replace chemotherapeutics (dewormers) in an effort to reduce worms’ impact on small ruminant production.

Alternatives include rotational grazing, nematophagous fungi, copper oxide wire particles, selective deworming, protein supplementation and genetic selection.

Alternatives to traditional forms of treatment work to minimize larval uptake, resulting in reduced worm burden. However, very few effectively remove entire populations of worms residing within an animal.

Decreased nematode populations aid in managing death loss and minimizing financial loss. However, subclinical symptoms of infections and the nutritional management needed to optimize production may play a more significant role in the profitability of small ruminant operations.

If you’ve attended a Penn State Extension event or participated in discussions on internal parasites, then you’re familiar with enemy No. 1, the barber pole worm.

Haemonchus contortus is classified as having a direct life cycle, lacking significant complexities. Its primary goal is to efficiently complete this direct life cycle and produce offspring for reinfection.

This parasite favors hot and humid ecosystems commonly found in the Southeastern United States. However, adaptation and persistence of the parasite have created concern in all corners of the country.

Seasonally dry or cold environments impede larval development and survival, hindering life-cycle completion. However, warm and wet weather in the summer allows for significant infections when environments are conducive.

Areas experiencing extended periods of cold or arid climate experience a reduced risk for extended exposure to the barber pole worm with decreased environmental survivability.

Independent of region, the significance of short-season haemonchosis has been observed in Canada, northern Europe and Scandinavia.

Classified as a hematophagous nematode, Hc reproduces and feeds in the abomasum of small ruminants.

Commonly referred to as the barber pole worm, its white and red spiraling color pattern is unique.

Spiraling coloration is depicted in mature females with blood-filled intestines appearing red and contrasting white ovaries intertwining the gastrointestinal tract.

Visible to the naked eye when mature, females measure 18 to 30 mm in length, with males measuring 10 to 20 mm. Physical attachment of Hc to the abomasum does not occur; however, Hc remain in the GI tract by constant swimming movement.

Detrimental feeding behavior is of greatest concern, with individual Hc blood consumption up to 0.05 milliliters per day.

Blood consumption is facilitated by a buccal lancet, which punctures the epithelium of the abomasal wall. Blood from this physical abrasion pours out and is consumed by adult worms.

Additional blood loss occurs from a lack of clotting due to calreticulin secretions by Hc, allowing blood to flow freely after feeding.

Feeding by Hc can result in anemia, hypoproteinemia and eventually death in serious Hc infections. Heavy infections of Hc may result in death in seven days with hyperacute infections.

Hyperacute infections occur after massive ingestion of larvae that begin feeding rapidly after development.

Young and immunocompromised individuals have the greatest risk of susceptibility when exposed to Hc. Severely infected animals express physical effects of the illness and will appear unthrifty, lethargic and thin, with an unwillingness to eat.

Additional physical indicators include submandibular edema, or bottle jaw, and whitening of mucosal tissues, like those around the eye.

Given the pathology of Hc, death loss and treatment contribute a sizable portion of financial loss for small ruminant producers. Subclinical infections result in production losses with reduced weight gain, milk production and wool growth.

Genetic selection for animals with immune systems specifically designed to prevent parasite establishment is a sustainable alternative to widespread dewormer use, promoting the future of a pasture-based sheep industry.

Selection for improved animals can be accomplished through purposeful record keeping and culling decisions based on treatment frequency. Additionally, this process can be accelerated through quantitative genetic selections made available through the national sheep improvement program.

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Camren Maierle is a Penn State Extension livestock educator in Mercer County with an expertise in small ruminants.

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