Gastro-Intestinal Parasites Co-Infection and their Interaction as Drivers of Host Heterogeneity in South African Communal Goat Populations

The study was conducted to evaluate how the concomitant infecting gastro-intestinal parasites (GIPs) modifies the intensity of infection, distribution pattern and host susceptibility to parasite within the South African communal indigenous goat population. A total of 288 goats were randomly sampled in different agro-ecological zones of South Africa. For each goat, the intensity of the GIPs was determined using a modified McMaster technique. Four subsets of data were used: the first included goats infected with single GIP species, either strongyles, Strongyloides papillosus, or Trichuris sp., the second, third and fourth considered goats co-infected with any two possible combinations of the three GIPs. The GLM procedures were used to analyse data. The three nematodes exhibited different age– intensity profiles. For single infections, infection intensity for strongyles and Trichuris sp., were higher (p<0.05) in young goats compared to other age groups. Co-infection by S. papillosus and Trichuris sp., strongyles and Trichuris sp. increased the infection intensity with the host age, but their pattern did not change (p>0.05). Strongyles intensity pattern in co-infection with either S. papillosus or Trichuris sp. did not change, as young goats exhibited higher (p<0.05) intensity than other age groups. The infection intensity for S. papillosus and Trichuris sp. between goat of different ages were similar (p>0.05) when co-infected with strongyles. Sex–intensity profile of all GIPs in single infections did not differ (p>0.05). Co-infection by S. papillosus and Trichuris sp. did not influence (p>0.05) the sex-intensity profile of these nematodes. Goats co-infected by strongyles with either S. papillosus or Trichuris, the intensity of these GIPs was high (p<0.05) in females compared to males. Multiple GIPs infections resulted in the accumulation of GIPs in the host population and variation in parasitism between goat ages and sexes. Concomitant GIP infections modify host susceptibility and influence heterogeneity amongst individual hosts.