Estimating the impact of Trypanosoma evansi infection (surra) on buffalo population dynamics in southern Philippines using data from cross-sectional surveys

Abstract

Despite the widespread problem with surra (Trypanosoma evansi) in livestock, there are no published studies on its impact on host populations, probably because of the large financial and time cost involved in performing longitudinal studies. During 2002-6, a cross-sectional survey for T. evansi infection involving 1,732 buffaloes from 71 villages in southern Philippines was carried out. Other livestock animals (horses, cattle and goats) in every surveyed village were also tested for infection with T. evansi but domestic buffalo were the primary survey target. Seroprevalence ranged from 6% to 21% and 13% to 100% for buffalo in low and high risk areas, respectively. Key demographic parameters were estimated from the age structured distributions of the sampled buffalo population for each sex. All areas were dominated by females (69%) and the annual calving rate for areas of 100% and low seroprevalence was 15% and 47%, respectively. Males were removed at a relatively high annual rate of 27% in all areas. In the main reproductive years (4-10) female removal/mortality was <1% and 10% for low and high risk areas, respectively. Older females were removed/died at a rate similar to males regardless of area. In high risk areas there were consistently more 2-year than 1-year old females and the reverse was true for the low risk areas. This implies that females were imported to the high risk areas for breeding. By assuming a stable age structure and similar size populations in each area, it was estimated that 28% of female calves need to be moved from low to high risk areas to maintain the observed age structure. In high-risk areas, surra imposes significant financial losses due to reduced fertility, high mortality/removal rate and the necessity to import replacement buffalo.

Models for Trypanosoma evansi (surra), its control and economic impact on small-hold livestock owners in the Philippines

“…Data from a 4-year (2002-6) survey of village buffaloes and other animal hosts from five provinces in Mindanao, Philippines were used to define the model framework (Dargantes et al, 2009). …”

“…Because buffalo were the primary survey target, relatively few non-buffalo hosts were sampled (see Table 2 in the accompanying paper by Dargantes et al (2009)). Using the observed seroprevalence in buffaloes from (Table 4) and observed seroprevalence for other host-species can be made.…”

“…Horses are most susceptible to surra, showing acute disease and high mortalities (Silva et al, 1995), while goats and pigs are also likely to be infected (Manuel, 1998;Reid, 2002;Dargantes et al, 2005: Holland et al, 2003. Reduced fertility and mortality were observed in buffalo populations in surra-high risk areas (Dargantes et al, 2009). However, despite the impact of surra on animal productivity, financial losses due to the disease are potentially underestimated due to insufficient data, misdiagnosis, remoteness of the affected areas, and reluctance of the farmers to report mortalities.…”

“…evansi conducted in Mindanao (Dargantes et al, 2009) was used to estimate parameters for the host population demographic and infectious disease models. Treatment costs and the benefits gained by animals achieving their full reproductive potential were included in the model as a measure of the productivity from village/small-hold farms in the Philippines.…”

The Effect of Papaya (Carica papaya L.) Leaf Extract to the Number of Trypanosoma evansi Steel in Liver and Kidney of Mice (Mus musculus L. 1758)

“…Growth of buffalo population in endemic areas lower 50% compared with areas that are not. Economic losses due to this disease is estimated at up to 158 000 USD per year [3]. In Indonesia, surra was reported by Direktorat Kesehatan Hewan [4] occurred on Sumba, East Nusa Tenggara in 2010 to 2011.…”