Microsatellite typing and population structuring of Trypanosoma evansi in Mindanao, Philippines

Abstract

Please cite this article as: McInnes, L.M., Dargantes, A.P., Ryan, U.M., Reid, S.A., Microsatellite typing and population structuring of Trypanosoma evansi in Mindanao, Philippines, Veterinary Parasitology (2010), doi:10.1016/j.vetpar.2011 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. (ADN)) in Mindanao, Philippines were each successfully genotyped using a suite of 7 25 polymorphic microsatellites. The study identified 16 multi locus genotypes (MLG) within the T. 26 evansi isolates and evidence of the spread of surra outbreaks from one village to another, most 27 likely due to the movement of infected animals. Genotyping provided evidence of population 28 sub-structuring with 3 populations (I, II and III (only 1 isolate)) identified. The most abundant 29 population was II, which was the predominant population in ADS and SDS (p=0.022). In 30 addition, buffalo mortality was statistically higher in outbreak areas associated with isolates from 31 population I (13.6%) than with isolates from population II (6.9%) (p=0.047). The present study 32 has highlighted the utility of microsatellite loci to improve understanding of the epidemiology of 33 T. evansi and in tracking surra outbreaks. 34 35 KEYWORDS 36Trypanosoma evansi, surra, epidemic, microsatellites, DNA, Mindanao, Philippines. 37 38Page 3 of 43 A c c e p t e d M a n u s c r i p t 3 Introduction 39Trypanosoma evansi is endemic in Africa, the Middle East, Central and South America, and 40 many parts of Asia including the Philippines (OIE, 2008 with an outbreak in the North Samar province reported to have caused buffalo mortalities in 47 excess of a thousand over a 6-month period (Cresencio et al., 1994; Manuel, 1998). 48Surra was first introduced into the Philippines in the early 19 th century with the 49 importation of infected cavalry horses from China by the American forces during the American-50Spanish war (Manuel, 1998). The initial and successive surra cases which occurred in the 51Philippines were predominately reported as high mortalities of equines (Manresa, 1935; Randall 52 and Schwartz, 1936; Manuel, 1998). Mindanao, the second largest and southernmost island in 53 the Philippine archipelago appeared to be free of surra until 1989 when the first reported cases of 54 surra (38% equine and bovine mortality) were recorded in the southern Mindanao province of 55 Sarangani (Mercado, R. pers. comm., 2010). Subsequent to the Sarangani outbreak, further surra 56 outbreaks have occurred in a range of Mindanao provinces (Fig. 1). At present, the economic 57 losses due to surra in Mindanao have been estimated at US$1.58 million per year from every 1...

Null allele, allelic dropouts or rare sex detection in clonal organisms: simulations and application to real data sets of pathogenic microbes

“…Combined with the absence of missing data, our criterion argues for allelic dropouts (model 1) up to 20-50% in this species. This is consistent with a recent study [31], where isolated T. evansi were genotyped using different loci from those presented here, showing perfect adequacy with a purely clonal population with 100% of superimposed points (not shown). Here the advice would be using such loci to genotype Sudanese isolates again.…”

“…Other data from African trypanosomes, the DNA of which was amplified directly from host blood (no isolation step), were also investigated. T. evansi from Sudan, the reproductive system of which remains unclear, though assumed to be clonal [30,31], was suspected to present many allelic dropouts, due to the presence of an abnormally high proportion of homozygous individuals without missing genotypes and substantial variance of F IS across loci, together with a Wahlund effect [32]. In T. congolense , strong heterozygote deficits were found [33], for which the authors proposed a highly inbred sexual mode of reproduction.…”

Population Genetics and Reproductive Strategies of African Trypanosomes: Revisiting Available Published Data

“…It is worth noting that a more recent study that used other loci in Asian T . evansi samples found data compatible with total clonality in that species (high and invariable heterozygote excesses) [ 70 ]. A more recent theoretical study [ 19 ] confirmed that allele dropouts can alone explain T .…”

Pathogenicity of Philippine and Indonesian Trypanosoma evansi Isolates in Mice and Their Responses to Trypanocides

“…Severe outbreaks of surra in the Philippines were reported in South Cotabato and Agusan del Sur, Mindanao between 1989-1994(McInnes et al 2012. The disease spread to other provinces in the following years.…”