Molecular and serological detection of Babesia bovis- and Babesia bigemina-infection in bovines and water buffaloes raised jointly in an endemic field

ROMERO-SALAS D; MIRA A; MOSQUEDA J; GARCÍA-VÁZQUEZ Z; HIDALGO-RUIZ M; ORTIZ VELA NA; PEREZ DEL LEON AA; FLORIN-CHRISTENSEN M; SCHNITTGER L

Congreso; International Congress on Tropical Veterinary Medicine, 2nd Joint AITVM-STVM Meeting; 2018

Babesia bovis and Babesia bigemina are causativeagents of bovine babesiosis, a tick-borne disease of tropical and subtropicalregions. Babesia spp. infection adversely affects cattle health and canbe fatal, resulting in considerable economic loss worldwide. Under endemicstability conditions, herds contain high numbers of chronically infected,asymptomatic carrier animals, in which no parasitemia is detected bymicroscopic blood smear examination. In addition to bovines, also waterbuffaloes are infected by both Babesia spp. commonly leading to a subclinicalinfection. The infection rate (by nPCR) and herd exposure (by IFAT) of bovinesand water buffaloes reared under similar field conditions in an area of endemicstability were determined and compared. In order to optimize direct parasitedetection, highly sensitive nPCR assays were developed and applied, allowingthe detection of as little as 0.1 fg DNA of each Babesia pathogen.Significantly lower percentages (p < 0.001) of seropositive water buffaloescompared to bovines were observed for B. bovis (71.4% vs. 98%) and B.bigemina (85% vs. 100%). Interestingly, in comparison, differences noticedbetween water buffaloes and bovines were considerably larger with directparasite detection by nPCR (16.2% vs. 82.3% and 24% vs. 94.1% for B. bovis andB. bigemina, respectively). As expected, bovines subjected to monthlyacaricide applications exhibited a significant lower infection rate asdetermined by nPCR than bovines not subjected to these measures (B. bovis 33.3%vs. 90.7%,p < 0.001; B. bigemina 80% vs. 96.5%, p < 0.001, fortreated vs. untreated animals). Interestingly no differences between thesegroups were observed with respect to seropositivity, suggesting similar ratesof parasite exposure (B. bovis 100% vs. 97.7%, p < 0.001; B.bigemina 100% vs. 100%, p < 0.001). Importantly, a significantly highernumber of water buffaloes as determined by nPCR were infected when rearedjointly with bovines not subjected to tick control than when reared jointlywith bovines subjected to tick control (B. bovis 31.6% vs. 9.5%, p <0.01; B. bigemina 42.1% vs. 9.5%, p < 0.01, for water buffaloesreared with untreated vs. treated bovines) and/or when reared without bovines (B.bovis 31.6% vs. 11.6%, p < 0.01; B. bigemina 42.1% vs. 20%, p< 0.01). In summary, our findings suggest that water buffaloes are much morecapable to limit or eliminate Babesia infection, possibly due to a morecapable immune defense. Furthermore, an increased Babesia spp. parasitereservoir of bovines seems to increase the infection rate of water buffaloeswhen both are reared on the same pasture.