Building a combined targeted selective treatment scheme against gastrointestinal nematodes in tropical goats

The design and validation of a combined targeted selective treatment (C-TST) scheme to control gastrointestinal nematodes (GIN) of goats under tropical conditions is described. A survey performed on 1585 goats (older than 4 months) from 103 smallholder subsistence farms from tropical México (Yucatán), showed the classical over-dispersion distribution of the GIN fecal egg excretions (FEC) indicating that most goats had a low excretion of eggs and only a few had high FEC. A second stage of the survey (20 farms) tested the association between FAMACHA© and packed cell volume (PCV) (n = 638) as well as FAMACHA© and FEC (n = 627). The survey showed that FAMACHA© was a good tool to identify anemic animals but no association was found with their FEC. As a result, we proposed to combine FAMACHA© with body condition score (BCS) to identify adult animals at risk of high GIN infections. The FEC was used to identify goats needing anthelmintic (AH) treatment. The C-TST scheme was surveyed in a goat farm (mean 138 adult goats/year) in Yucatán for 6 years (8292 events recorded). In that period, the mean number of goats left without AH treatment was 57.4%. Meanwhile, nearly 30% of the goats needed only one treatment per year. Less than 15% of the goats required 2 or more treatments per year. Besides, the AH doses were distributed amongst small number of animals every month throughout the year. Thus, under the browsing conditions of Yucatán, México, the combination of BCS and FAMACHA© can be used as a screening procedure to identify animals at risk of severe GIN infections and the FEC help to reduce the number of goats treated per year with no apparent negative consequences on the goats.