Semi-arid Zone, Pastoralist Producers

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Typical Problems In This Area

1. Due to the uneven distribution of rainfall during the year, there are times when grazing is in short supply and animals suffer from nutritional stress.

2. Worm burdens often build up slowly and coupled with poor feeding lead to a chronic condition.

3. Trichostrongylus, Haemonchus and Oesophagostomum can all be present and contribute to a generalised parasitic gastroenteritis.

4. During the dry seasons invading larvae may enter a period of delayed development in the animal (Inhibited worms).

5. Although overall stocking rates may be low, these can be locally high around watering points and bomas.

6. Toxocara may be a problem in young suckling calves.

7. Coenuriasis may be quite common in sheep and goats.

Features Of The Area That Can Help In Control

1. Transmission is seasonal and a significant portion of the year is too dry for worm larvae to survive on pasture.

2. When inhibited worms are present, drug treatments can be efficiently targeted at these.

3. Overall stocking rates are low.

4. There is little need for frequent anthelmintic treatments, so risk of developing anthelmintic resistance is low.

5. Most stock kept are of indigenous, worm-resistant breeds.

Control Methods That May Be Useful

· Frequent observation of individual animals and treating only clinical cases.

· Since rates of infection are seasonal, treatments can be targeted at times of year when there are peaks of infection.

· Since periods of poor grazing and nutritional stress are seasonal, treatments can be timed to alleviate chronic infections.

· At certain times of year a large part of the overall worm population is present as inhibited larvae. By correctly applying an effective drug at this time, infection rates can be reduced for the ensuing dry season. (treatment against inhibited worms).

· Keeping local breeds of animals rather than exotics can lead to higher production at lower treatment costs (Genetic Resistance).

· Specific treatments to control Toxocara may need to be carried out where this is a persistent problem.