Dear Daktari, I have been keeping sheep and goats in a ranching system in Kajiado County for years now. However, the last three years have seen me lose my animals to what my vet calls bottle jaw. The sheep and goats develop a swollen neck. My vet says this is due to stomach worms. Initially, I was deworming by myself and it was effective but the vet advised that I Iet him do it. This together with rotational grazing has reduced the problem to some extent. What are these worms that cause the neck and not the stomach to swell? [Jonathan Memusi, Kajiado County]
Thanks Memusi for the question. This is most likely a roundworm that is common in sheep and goats. Haemonchus contortus is its scientific name; and Haemonchosis is the disease condition it causes. These worms measure up to 2.5 centimetres and occur in the abomasum or fourth stomach of sheep and goats. Female worms have a red and white striped appearance, hence the name ‘barber's pole’ worm. This worm is the most economically significant internal parasite of sheep and goats not only in Kenya but throughout the world. Recently its devastating effects have been worsened by development of resistance to dewormers (anthelmintics). Haemonchosis is a deadly disease if not timely and effectively managed.
All ages of sheep and goats are susceptible, but the condition is fatal in weaned animals where it can kill within a very a short time. Overgrazing, overstocking and poor nutrition can increase susceptibility to infestation with this worm. The infective L3 larvae is ingested during grazing on contaminated pastures. This larvae will mature in one of the ruminant stomachs (abomasum), lay eggs which are passed out together with feaces onto pastures where they grow (molt, within three to four days) into infective larvae that climb onto blades of grass. Although this worm prefers warm and moist climatic conditions it can still survive in a wide range of weather conditions. In extreme cold weather the larvae can become metabolically inactive to survive through.
A sheep or goat suffering from haemonchosis will have stunted growth or will lose weight. The clinical signs are determined by the worm load. With high appetite for blood hookworms will cause anaemia. Sub mandibular edema or bottle jaw is characteristic of this condition that sometimes gives it a name – “bottle jaw”. As the condition progresses the animal becomes weak and my collapse and die if not treated. Diarrhoea is not normally observed with haemonchosis and this has been blamed for its “silent” nature until it is very late. Diagnosis is guided by the clinical signs especially the anaemia – pale mucous membranes. FAMACHA is an on-farm chart that uses the level of paleness of mucous membrane to inform strategic deworming. Another technique that can be used to determine the worm load is McMaster’s technique.
Management and Prevention
Haemonchus is prevalent in warm climatic regions like the tropics and sub tropics. There are several trains of Haemonchus that are resistant to anthelmintics hence deworming must be strategic. There is a newly developed vaccine but it is yet to permeate the market. Management of Haemonchosis is through early diagnosis and treatment, strategic prevention (strategic deworming) and pasture management. Rotational grazing, right stocking level can help reduce the level of pasture contamination and hence levels of infection.
[Dr Othieno is a veterinary surgeon and the head of communications at the Food and Agriculture Organisation of the United Nations (FAO) Kenya. The views expressed here are not necessarily those of FAO]