Detection of an Ehrlichia bovis-like organism in cultured buffalo monocytes

Molecular and serological detection of Anaplasma infection in carrier cattle in north India

Anaplasma marginale infection in cattle (n = 216) in the states of Uttar Pradesh and Uttarakhand, North India was screened by microscopy and nested-polymerase chain reaction (PCR). Two recombinant proteins viz. major surface protein (MSP) 5 and MSP2 of A. marginale were expressed in Escherichia coli and their potential in the detection of antibodies to Anaplasma species in the cattle was evaluated by immunoglobulin G-enzyme linked immunosorbent assay (IgG-ELISA). The MSP5 IgG ELISA results were compared with competitive (c) inhibition ELISA. Microscopy being the least sensitive diagnostic test detected 12.0% of animals positive for A. marginale infection while nested-PCR detected 87.9% of these animals as positive for A. marginale infection. The recombinant MSP5 antigen showed positive reactivity in 170/190 nested-PCR confirmed positive animals (sensitivity 89.5%) with specificity of 77.0%. In comparison, the recombinant MSP2 antigen showed lesser sensitivity and specificity of 79.0% and 69.2%, respectively. The cELISA was more sensitive and specific than IgG-ELISA. However, molecular detection by msp5 nested-PCR was highly sensitive and reliable for detection of carrier cattle for Anaplasma infection. The study indicated that a large cattle population (87.9%) was carrier for A. marginale infection in this region of the country.

Molecular characterization of South Indian field isolates of bovine Babesia spp. and Anaplasma spp

Ticks and tick-borne diseases (TTBDs) are considered major causes of economic loss in the livestock sector which incur an annual control cost estimated at US$ 498.7 million in India. Among these diseases, babesiosis, theileriosis and anaplasmosis are listed among the top ten livestock diseases in India and cause significant mortality and morbidity among cattle. However, molecular characterization of bovine Babesia and Anaplasma species are scant; thus, the aim of this study is to perform molecular characterization of field isolates of Babesia spp. and Anaplasma spp. infecting bovines in Kerala, South India. Blood smears and whole blood samples were collected from a total of 199 apparently healthy adult female cattle in Kerala. Based on microscopy, Babesia spp., Theileria orientalis and Anaplasma spp. organisms were detected in 9 (4.5%), 40 (20%) and 6 (3%) samples, respectively. Genus-specific polymerase chain reactions for amplification of 18S rRNA of Babesia spp. and 16S rRNA of Anaplasma spp. revealed positive results with 18 (9%) and 14 (7%) samples. The phylogenetic analysis of 18S rRNA gene sequences of Babesia spp. confirmed the existence of two different populations of Babesia spp. circulating in the blood of infected cattle viz., Babesia bigemina and a Babesia sp. genetically related to Babesia ovata. Further phylogenetic analysis using rap-1a sequences of isolates of B. bigemina revealed higher levels of genetic heterogeneity. However, the field isolates of B. bigemina displayed only slight heterogeneity when the rap-1c gene was examined. Polymerase chain reaction followed by sequencing and phylogenetic analysis of 16S rRNA gene of Anaplasma spp. revealed the existence of Anaplasma marginale, Anaplasma bovis and Anaplasma platys in bovines in South India. Based on msp4 gene sequences, all the field isolates of A. marginale from Kerala were clustered in a single clade with others isolated from around the world. To our knowledge, this study forms the first report on occurrence of B. ovata-like parasites and A. platys in cattle from India.

Enzootic transmission of Anaplasma bovis in Nantucket cottontail rabbits

Serological studies of cottontail rabbits sampled from Nantucket Island, Mass., have suggested exposure to at least two ehrlichiae. The agent of human granulocytic ehrlichiosis (Anaplasma phagocytophilum) is intensely enzootic in rabbits there, but the identity of the other ehrlichial infection remains undescribed. We sampled rabbits over five transmission seasons and tested their blood and tissues for evidence of infection using PCR targeting an Ehrlichia genus-wide 16S rDNA target. Sequence analysis of positive amplicons revealed the presence of Anaplasma bovis, an agent not known to be present in North America. The average annual prevalence of A. bovis within rabbits, as determined by PCR of blood samples, was 18%. Haemaphysalis leporispalustris appears to serve as vector. The public health (human or veterinary) significance of this finding remains speculative.