Document Type Master's Dissertation Author Vatta, Adriano Francis URN etd-02232003-233622 Document Title Incidence, clinical appraisal and treatment of haemonchosis in small ruminants of resource-poor areas in South Africa Degree MSc Department Veterinary Tropical Diseases Supervisor
Advisor Name Title Prof R C Krecek Keywords
- body condition scores
- eye colour chart
- anthelmintic resistance
- clinical assay
- Haemonchus spp
- faecal nematode and trematode egg counts
Date 1900-08-01 Availability unrestricted AbstractA novel clinical assay for the assessment and subsequent treatment of Haemonchus infection in sheep to slow down the development of anthelmintic resistance – the FAMACHA©, system – has been developed, tested and validated in South Africa. The system is based on a colour chart with five colour categories depicting varying degrees of anaemia that are compared with the colour of the conjunctival mucous membranes of sheep. The animal is then scored from severely anaemic (pale) through anaemic to non-anaemic (red) and those animals considered in danger of succumbing to the effects of haemonchosis are treated. This method was tested in the present study in goats and sheep farmed under resource-poor conditions in South Africa.
The diversity and predominance of nematode genera in goats and sheep at Rust de Winter, Gauteng Province, in goats at Impendle, KwaZulu-Natal Province, and in goats and sheep at Kraaipan, North-West Province, were determined by means of a longitudinal study of the nematode faecal egg counts (FECs) and differential third-stage larvae. The animals were bled for haematocrit determination, scored for pallor of ocular mucous membranes using the FAMACHA© method, and body condition scored. A longitudinal study of the pooled trematode FECs was conducted at the same time.
Lower haematocrit values were registered for the goats during periods of heavier Haemonchus infection, which periods occurred from December/January to March for Rust de Winter; from December to March/April for Impendle; and from November/December to February or April for Kraaipan. For the sheep, the periods of heavier Haemonchus infection occurred from October to March at Rust de Winter and from September/October to February or April at Kraaipan. There was agreement too between the lower haematocrits and paler mucous membranes scored according to the FAMACHA© method.
Analyses in goats performed during the summers of 1998/1999 and 1999/2000 show a test sensitivity of 76% and 85%, respectively, meaning that the system may be used to identify correctly 76% to 85% of those animals in need of treatment with an anthelmintic. However, the test specificity remains low at 52% to 55%. This means that a large proportion of those animals that would not require treatment would in fact be treated. On the other hand, when the use of the FAMACHA© system is compared with conventional dosing practices where all the animals are treated, using the FAMACHA© system would result in a large proportion of the animals being left untreated. The untreated animals are then able to deposit the eggs of anthelmintic-susceptible worms on the pasture, while the treated ones should pass very few ova, given an effective anthelmintic. This maintains a reservoir of susceptible larvae in refugia, and should slow down the development of anthelmintic resistance.
The use of the FAMACHA© system may be recommended as part of an integrated approach to worm control in the resource-poor areas studied and may have wide application in the tropics and subtropics of sub-Saharan Africa and elsewhere.
Seasonal variations in body condition were evident in the goats at Impendle with the animals showing lower body condition scores (BCS) from June to September. The sheep at Kraaipan showed lower BCS from July to December. The small ruminants at Rust de Winter did not show clear seasonal variations, although the goats at Rust de Winter showed lower BCS from mid-July to early December and the sheep from August to mid-February. Although body condition was maintained by the goats at Kraaipan, the scores remained low overall. The BCS for Rust de Winter where the animals were grazed on a private farm were generally higher than those of the other sites, where communal grazing is practised.
The amphistome FECs followed a seasonal pattern, with an increase in the counts during the warmer months of the year (September to April). The study seems to indicate a different pattern of infection in goats raised under resource-poor conditions in South Africa from that on commercial farms, where outbreaks of clinical paramphistomosis occur during autumn and winter.
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