Impact of GI Parasites on Ruminants

Factors affecting parasitic infections

1. Climatic factors
   High air temperature helps increase the activity of some parasites and their reproduction in pastures. It was found that the number of H. contortos larvae per kilogramme of herbage was 1,086 larvae at 45°C, and then decreased to only 512 larvae at 15°C under similar grazing conditions.

1. Soil factors
   Parasitic infections are more frequent in clay soils than in sandy soils. This is due to the low humidity in sandy soils, as well as the possibility of sand drift, which helps cover the lower part of the plant where the larvae infest the host.
2. Animal factors
   
   1. Herd size: With high grazing density, there is a greater chance for parasite infestation, as the animals, in this case, have to consume the plant to a short distance from the soil surface, which increases the severity of infestation due to the increased number of larvae in this lower part of the plant.
   2. Age of animals: The response of animals (cattle) to parasitic infection decreases as they age. Also, animals that have been previously infected with parasitic infections are more resistant to new infections.

Effect on physiology

The GI parasites affect an animal’s feed intake to a varying extent depending on the magnitude of infestation.

The parasites residing in the true stomach (abomasum) such as H. contortus and O. ostertagia may cause damage to the HCL-secreting glands. As a result, the pH level in the gastric liquors increases to about seven or more, thereby leading to diarrhoea and weight loss. This is due to the fact that the increased pH will lead to increased production of gastrin hormone in the stomach, thereby increasing secretion of water from the liver, pancreas and the distal part of the small intestines which- in turn- causes diarrhoea and weight loss.

The parasites residing the small intestines such as T. colubriformis cause atrophy of the intestinal villi and hence reduces the ability to increase the surface area available for absorption and utilisation of feeds. In extreme cases, these parasites may cause damage to the intestinal wall itself and allow the passage of immunoglobulins from the blood plasma to the gastric cavity with an eventual loss of these immunoglobulins through faecal excretion and thus decrease the animal’s ­resistance to the microbial diseases.

Internal parasites also affect digestion and utilisation of dietary proteins, due to the decreased feed intake and the need for the animal to use feed proteins as a compensatory source of energy. Utilisation of other nutrient elements such as calcium and phosphorus may also be affected by parasite infestation, which adversely affects bone formation and causes ­rickets and other disease problems.

The low growth rate, in this case, is attributed to the effect of parasites on animal physiology and feed utilisation.

Parasite infections also affect milk production in cattle, which is reduced by about 3kg per day, in addition to the detrimental effect of the parasites on the reproductive efficiency of the herd, as evidenced by the low fertility rate, the reduced growth rate of the foetus and its birth weight.

In some critical cases, the parasitic infection may cause animal death, particularly in tropical and subtropical grazing areas where the climatic and nutritional factors in these areas predispose the animal to large numbers of parasitic larvae. Mortality occurs in the range of 10-20% in cattle.

Anti – parasitic drugs for Parasite Control in Ruminants

Anti-parasitic drugs are an important part of parasite control in the ruminants. Strategic use of anti-parasitic drugs is necessary to ensure effectiveness of treatment and to slow down the rate of drug resistance.

YORS offers a Wide range of anti- parasitic drugs that cover a broad range of diseases caused by parasites. YORS also have Different Anti – Parasitic Drug formulations to suit different dosage regimen for livestock.