Internal and External Parasite Control in Cattle

Patrick Davis, Ph. D.

West Central Missouri Regional Extension Livestock Specialist

Internal and external parasites are a problem to cattle which can reduce productivity and profitability of a cattle operation.  Specifically the internal parasites affect the gastrointestinal tract by damaging and irritating the stomach and intestinal lining or mucosa.  This results in decreased digestion and absorption of nutrients in these areas as well as protein and blood loss.  These results cause further production losses such as decreased feed intake, reduced weaning weight, poorer feed efficiency, reduced milk production and reduced reproductive performance.  Therefore this discussion will identify types and symptoms of internal and external parasites as well as ways to diagnose and treat the parasite problems.

Internal Parasites

One type of internal parasite that causes problems in cattle is worms.  The most common worm that affects cattle is the brown stomach worm.  This worm is transmitted between cattle through feces and the eating of contaminated grass.  Symptoms associated with this worm are diarrhea, reduced appetite, anemia, bottle jaw and rapid weight loss. The barber’s pole worm is another worm that could be a problem for cattle in the stomach.  This is a warm weather parasite that sucks blood which gives it the appearance of looking like a barber’s pole.  Since this worm can cause a significant amount of blood loss a small number of these worms can lead to acute symptoms of severe anemia and death.  Another warm season worm that causes blood loss is hook worms which affects the small intestine.  Also some other worms that disrupt intestinal function are the whip, wire, and tape worms.   

Coccidia is another harmful internal parasite to cattle.  It is a protozoan that infects the interior cell lining of the lymphatic blood vessels in the distal small intestine, cecum, and proximal colon.  This protozoan causes enteritis in these regions of the intestine resulting in bleeding which causes the animal to have bloody scours a symptom of coccidia.  The disease coccidiosis, which results from coccidia, is enhanced by stresses of weaning such as food and water deprivation and shipping.  Therefore cattle producers need to pay close attention to cattle at weaning time for coccidiosis symptoms and maybe use anticocidial drugs to prevent against coccidiosis.  Also worm infestations can enhance the likelihood of coccidiosis so when you see symptoms of worm issue you should also check for coccidia.

External Parasites

One type of external parasite that causes problems to cattle is flies.  Horse, deer and yellow flies bite cattle and transmit blood borne disease such as anaplasmosis which is a disease that can affect cattle operations.  Pinkeye is another major issues with cattle operations and its extent and severity is increased with the presence of face flies.  Another fly that shows up in the warmer months is horn flies and their presence is linked with lower gains and milk production.  Heel fly larvae or grubs will migrate to the top of the cow and damage the hide.  In rare occasions these grubs could migrate to the spinal cord causing paralysis and eventually death.

Other types of external parasites are lice, mites, and ticks.  Lice feed on hair, skin and blood. Symptoms of lice is lameness, dermatitis, hair loss, allergic responses, and skin crusting or scabbing.  Like lice, mites cause skin irritation and scabbing.  Furthermore heavy infestation of mites can lead to lesions.  Also mites can enter the respiratory passages, ear canals, and internal organs and cause damage.  Finally ticks like lice and mites will cause damage to cow hides.  Furthermore ticks feed on blood and transmit pathogens and disease through the blood.

Diagnosis and Treatment  

When diagnosing and treating a parasite problem consult a veterinarian and develop a diagnosis and treatment plan prior to when internal and external parasites are a problem.  To diagnose internal parasites you can watch for symptoms but in most cases a fecal egg count is your best option.  Unless you have the skills to conduct this process and microscope to look at the samples you need to consult a veterinarian and use their microscope and expertise to identify the internal parasite problem.  Once the parasite is identified select the proper dewormer to treat the problem.  Dewormer product and form of treatment should be changed every 2 to 3 years to cut down on resistance problems.  External parasite diagnosis is through visual appraisal.  If an internal and external parasite problem is identified the producer my want to use a combination treatment for internal and external parasites.  If coccidia is determined then anticoccidial drugs such as corid, deccox, bovatec, rumensin, and sulfa-nox could be used for treatment.

Insecticides are used to treat external parasites.  The various types are injectibles, fly tags, baits, boluses, dips, dust, pour-ons, spot-ons, sprays, rubs, and feed additive in mineral or feed supplements.  When using these products it is important to read the labels and apply the product correctly to get the desired response.  Also with products that you have to reapply to the applicator like rubs, dusts and other products make sure the applicator has the correct amount of insecticide on it to get the desired response.  Also with feed additives make sure that the animal is consuming the correct amount to get the desired response. 

In the diagnosis, treatment and control of internal and external parasites work closely with your veterinarian to identify the best protocol for your cattle operations.  For more information contact your local MU Extension Center.