Molecular epidemiological insights into Trypanosoma vivax in Argentina: From the endemic Gran Chaco to outbreaks in the Pampas

Abstract

Argentina is a home to millions of beef and dairy cattle and is one of the world's major exporters of meat. In the present study, Trypanosoma vivax was prevalent (2016–2018) in two major livestock farming regions, the Gran Chaco and the Pampas. In the Gran Chaco, 29% and 51% of animals (n = 72, taurine x zebuine crossbreed) were, respectively, positive by TviCATL‐PCR and the more sensitive fluorescent fragment length barcoding (FFLB) method. While 18.4/38.8% of breeding cows (n = 49) tested positive by PCR/FFLB, infection increased to 52.2/78.3% in an outbreak of acute infection in steers (n = 23, taurine breed) brought from a non‐endemic area. In the Pampas, overall infection rates in dairy cows (n = 54, taurine breed) were comparable (p > .01) between PCR (66.7%) and FFLB (62.9%) and showed a remarkable increase (PCR / FFLB) from 48.3/44.8% in 2017 to 88/84% in 2018. Infected dairy cattle exhibited anaemia, fever, anorexia, enlarged lymph nodes, emaciation and neurological signs. In contrast, beef cows (taurine x zebuine crossbreed) from the Pampas (n = 30) were asymptomatic despite exhibiting 16.7% (PCR) and 53.3% (FFLB) infection rates. Microsatellite genotyping revealed a remarkable microheterogeneity, seven genotypes in the Gran Chaco, nine in the Pampas and five shared between both regions, consistent with regular movement of T. vivax infected livestock. Data gathered in our study support the Gran Chaco being an endemic area for T. vivax, whereas the Pampas emerged as an outbreak area of acute infection in dairy cattle with critical negative impact in milk production. To the best of our knowledge, this is the first molecular study of T. vivax in Argentina, and results indicated the need for preventive measures to control T. vivax spread from the Gran Chaco to vast livestock farming areas across Argentina.

Improved Serodiagnosis ofTrypanosoma vivaxInfections in Cattle Reveals Higher Infection Rates in the Livestock Regions of Argentina

“…, however, to date Buenos Aires has no cases of T. vivax, so the assessment in the provinces of Cordoba and Santa Fe covers almost 70% of the dairy basin, where T. vivax is endemic(17).Our results are comparable to those of other studies in South America, highlighting the high prevalence of this disease in endemic regions. An epidemiological study in the Pantanal region of Brazil using indirect ELISA reported an average seroprevalence rate of 56%(41).…”

“…Significant economic impacts have been caused by losses in dairy cattle infected with T. vivax , leading to the treatment of entire herds and resulting in a substantial reduction in milk production from affected herds (17,48). In this study, we demonstrated high seroprevalence of the disease in an affected region, suggesting a possible spread of the disease in the southern and eastern areas of the Pampas region, as observed by other authors (17,51).…”

“…Argentina is one of the world’s leading beef exporters, with northeastern and central-eastern areas being vital livestock production zones. Despite initial reports in Argentina, T. vivax was recently identified through molecular methods in 2018 (16) and has been associated with acute disease in dairy cattle in the Pampas region, having a substantial economic impact (17).…”

“…Molecular assays; such as conventional PCR; have successfully detected T. vivax (4,11,17). However, these assays are costly and require specialized laboratories for execution, rendering them inaccessible to field veterinarians and dairy farm owners.…”

Comparative Sensitivity and Specificity of the 7SL sRNA Diagnostic Test for Animal Trypanosomiasis

“…AT is considered a major constraint on agricultural production in Sub-Saharan Africa; it is estimated to infect over 70 million cattle annually and is responsible for production losses that total billions of dollars per year ( 2 , 3 ). T. vivax is a cause of concern in Central and South America where its geographical distribution has grown in recent years ( 4 – 6 ). Current estimates indicate that over 11 million cattle are at risk of infection in the extensive cattle ranching areas of the Brazilian Pantanal and Bolivian lowlands alone ( 5 ).…”