Spatial and temporal epidemiology of bovine trichomoniasis and bovine genital campylobacteriosis in La Pampa province (Argentina)

Abstract

The venereal diseases bovine trichomoniasis (BT) and bovine genital campylobacteriosis (BCG) cause economic losses in endemic areas like La Pampa province in Argentina, where beef cattle are usually managed extensively. This study used data compiled under a Provincial Programme for the Control and Eradication of BT and BGC (PCE) to determine the spatio-temporal distribution of these diseases and identify spatial clusters. The study population comprised 29,178 non-virgin bulls drawn from 3766 herds, tested for BT and BGC in 2010. Preputial smegma samples were cultured for BT detection, while BGC was diagnosed by direct immunofluorescence testing of these samples. Campylobacter fetus infection was detected in 1.5% of bulls and 2.3% of herds, and Tritrichomonas foetus infection was found in 1.1% of bulls and 5.1% of herds. The proportion of positive tests was highest in February for BT, while in April it was highest for BCG, and was inversely related to the number of tests, which was greatest during the breeding season (spring). An elliptical spatial cluster of high risk for BGC and a circular cluster for BT were both identified in the south of La Pampa province, which could not be explained by cattle herd density. The spatial and temporal patterns identified in this study provide baseline data for monitoring the success of BT and BGC control activities in La Pampa.

Introduction

Bovine trichomoniasis (BT) and bovine genital campylobacteriosis (BGC) are venereal diseases caused respectively by the flagellate protozoan Tritrichomonas foetus (Skirrow and BonDurant, 1988) and the Gram (-) Campylobacter fetus subspecies venerealis (Eaglesome and Garcia, 1992). Both agents are transmitted mainly during coitus, and colonize the reproductive tract of bulls and cows. In cows, infection can cause reproductive failures, including repeat of estrus, early embryonic death and abortions; in bulls, however, both infections are typically asymptomatic (Anderson, 2007, Mancebo et al., 1995). Infected bulls and cows can become long-term carriers (Corbeil et al., 2003).

In areas where beef cattle are mainly managed intensively, artificial insemination (AI) has largely displaced natural breeding; this tends to control the factors which typically favour these diseases (BonDurant, 2005). As a result, the incidence of both diseases in Europe, for example, is very low or negligible. However, in areas where production systems are typically extensive, based on communal pastures and natural breeding, incidence remains high (Gay et al., 1996, Mshelia et al., 2010). Moreover, it has been reported that the vaccines developed to date are unlikely to induce an effective immune response under field conditions, thus hindering the implementation of effective control plans in endemic areas (Cobo et al., 2004, Villarroel et al., 2004). Consequently, both diseases continue to be associated with economic losses due to breeding failure.

In Argentina BT and BGC are considered endemic and their adverse impact on the economy is considerable (Mardones et al., 2008, Jiménez et al., 2011). La Pampa province includes around 6% of the national herd (SENASA, 2012), and beef cattle production accounts for almost 16% of the province's gross domestic product (DGEC, 2012). Awareness of the economic importance of this sector led in 2006 to the implementation of a Provincial Programme for the Control and Eradication (PCE) of BT and BGC. Participation in the programme is compulsory for all cattle farmers; however, due to the shortage of epidemiological and economic data on the regional incidence of the two diseases, only the control phase has been implemented so far, and the culling of positive bulls remains voluntary.

Recent research has recognized the importance of geographical location in identifying clusters of high-risk areas, which is essential to improve the intervention efforts (Kazembe et al., 2009). Geographical location is a proxy of factors that affect the prevalence of the disease. Spatial heterogeneity in these factors influences the disease transmission pattern (Allepuz et al., 2011). Consequently, efforts to reduce the prevalence of BT and BGC in La Pampa should include research on the influence of location on bovine diseases. These kinds of analyses are scarce for bovine venereal diseases and have been focused on spatial modelling of BT (Szonyi et al., 2012). Moreover, BT and BGC are influenced by some common factors such as herd size, animal density and pasture management. If similar patterns of geographical variation of both diseases could be identified, it might provide evidence of shared risk factors in La Pampa (Knorr–Held and Best, 2001).

The data compiled under the PCE provide reliable, essential information regarding the distribution and epidemiology of these diseases in La Pampa. They should therefore serve as the basis for decisions regarding the prevention, control and potential eradication of BT and BGC. Therefore, the objective of the present study, using official data from the PCE, was to determine the prevalence and spatio-temporal distribution of these diseases in the province of La Pampa.