Molecular and serological detection of Babesia bovis- and Babesiabigemina-infection in bovines and water buffaloes raised jointly in anendemic field

Authors: ROMERO-SALAS, DORA - University Of Veracruz; MIRA, ANABELA - Consejo Nacional De Investigaciones Científicas Y Técnicas(CONICET); MOSQUEDA, JUAN - Autonomous University Of Querétaro; GARCIA-VAZQUEZ, ZEFERINO - Instituto Nacional De Investigaciones Forestales Y Agropecuarias (INIFAP); Perez De Leon, Adalberto - Beto; FLORIN-CHRISTENSEN, MONICA - Consejo Nacional De Investigaciones Científicas Y Técnicas(CONICET); SCHNITTGER, LEONHARD - Consejo Nacional De Investigaciones Científicas Y Técnicas(CONICET)

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2015
Publication Date: 2/15/2016
Citation: Romero-Salas, D., Mira, A., Mosqueda, J., Garcia-Vazquez, Z., Perez De Leon, A.A., Florin-Christensen, M., Schnittger, L. 2016. Molecular and serological detection of Babesia bovis- and Babesiabigemina-infection in bovines and water buffaloes raised jointly in anendemic field. Veterinary Parasitology. 217:101-107.

Interpretive Summary: Bovine babesiosis is a deadly disease of cattle caused by several species of single-celled parasites found in the blood, or hemoparasites, belonging to the genus Babesia, including B. bovis and B. bigemina, which are transmitted to susceptible animals by ticks. Other livestock, like the water buffalo, can be infected with B. bovis and B. bigemina, but generally don’t show signs of disease. The infection rate in cattle and water buffaloes sharing the same habitat where they were exposed to B. bovis and B. bigemina through the bite of infected ticks was determined and compared using a test for antibodies against, and a sensitive molecular assay to detect nucleic acid of these hemoparasites. Signi'cantly lower percentages of antibody-positive water buffaloes compared to bovines were observed for B. bovis (71.4% vs. 98%) and B. bigemina (85% vs. 100%). By comparison, differences noticed between water buffaloes and bovines were considerably larger with direct parasite detection by the molecular assay (16.2% vs. 82.3% and 24% vs. 94.1% for B. bovis and B. bigemina, respectively). Bovines subjected to monthly acaricide applications, that is treatments to kill the tick vectors, exhibited a signi'cant lower infection rate as determined by the molecular assay than bovines not subjected to these measures (B. bovis 33.3% vs. 90.7% and B. bigemina 80% vs. 96.5%, for treated vs. untreated animals). No differences between these groups were observed with respect to being antibody positive, suggesting similar rates of hemoparasite exposure (B. bovis 100% vs. 97.7%; B. bigemina 100% vs. 100%). Importantly, a signi'cantly higher number of water buffaloes as determined molecularly were infected when reared jointly with bovines not subjected to tick control than when reared jointly with bovines subjected to tick control (B. bovis 31.6% vs. 9.5% and B. bigemina 42.1% vs. 9.5%, for water buffaloes reared with untreated vs. treated bovines) and/or when reared without bovines (B. bovis 31.6% vs. 11.6%; B. bigemina 42.1% vs. 20%). An accumulation of positivity for antibodies and a decline of infection rates were observed in older animals, while differences observed with regard to gender may warrant further investigation. These 'ndings suggest that water buffaloes are much more able to limit or eliminate Babesia infection, possibly due to a more capable immune defense. Furthermore, an increased Babesia spp. parasite reservoir of bovines seems to increase the infection rate of water buffaloes when both are reared on the same pasture.

Technical Abstract: tBabesia bovis and Babesia bigemina are causative agents of bovine babesiosis, a tick-borne disease of cattlein tropical and subtropical regions. Babesia spp. infection adversely affects cattle health and can be fatalresulting in considerable economic loss worldwide. Under endemic stability conditions, herds containhigh numbers of chronically infected, asymptomatic carrier animals, in which no parasitemia is detectedby microscopic blood smear examination. In addition to bovines, also water buffaloes are infected by bothBabesia spp. commonly leading to a subclinical infection. The infection rate (by nPCR) and herd exposure(by IFAT) of bovines and water buffaloes reared under similar field conditions in an area of endemicstability were determined and compared. In order to optimize direct parasite detection, highly sensitivenPCR assays were developed and applied, allowing the detection of as little as 0.1 fg DNA of each Babesiapathogen. Significantly lower percentages (p < 0.001) of seropositive water buffaloes compared to bovineswere observed for B. bovis (71.4% vs. 98%) and B. bigemina (85% vs. 100%). Interestingly, in comparison,differences noticed between water buffaloes and bovines were considerably larger with direct parasitedetection by nPCR (16.2% vs. 82.3% and 24% vs. 94.1% for B. bovis and B. bigemina, respectively).As expected, bovines subjected to monthly acaricide applications exhibited a significant lower infec-tion rate as determined 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, for treated vs. untreated animals). Interestingly no differ-ences between these groups were observed with respect to seropositivity, suggesting similar rates ofparasite exposure (B. bovis 100% vs. 97.7%, p < 0.001; B. bigemina 100% vs. 100%, p < 0.001). Importantly, asignificantly higher number of water buffaloes as determined by nPCR were infected when reared jointlywith bovines not subjected to tick control than when reared jointly with bovines subjected to tick con-trol (B. bovis 31.6% vs. 9.5%, p < 0.01; B. bigemina 42.1% vs. 9.5%, p < 0.01, for water buffaloes reared withuntreated 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). An accumulation of seropositivity and a decline of infection rateswere observed in older animals, while differences observed with regard to gender may warrant furtherinvestigation. In summary, our findings suggest that water buffaloes are much more capable to limit oreliminate Babesia infection, possibly due to a more capable immune defense. Furthermore, an increasedBabesia spp. parasite reservoir of bovines seems to increase the infection rate of water buffaloes whenboth are reared on the same pasture.