Outbreak of anaplasmosis associated with novel genetic variants of Anaplasma marginale in a dairy cattle.

During early lactation, dairy cows may present a transient immunosuppressive state and develop anaplasmosis caused by Anaplasma marginale. In this study, clinical anaplasmosis in dairy cattle in the Thrace region of Turkey was investigated with respect to within-herd prevalence, vertical transmission, and genetic diversity. In March and September 2015, thirty lactating cows showed primary clinical signs of anaplasmosis, including fever, anaemia, decreased milk yield, anorexia, and laboured breathing. Symptoms disappeared in most cows after administration of long-acting oxytetracycline, but nine of them (30%) died. Following diagnosis based on clinical signs, microscopy and molecular findings, blood samples were collected from apparently healthy lactating cows (n=184), pregnant heifers (n=39) and newborn calves (n=24). DNA was extracted from each sample and analyzed for the presence of major surface proteins (MSPs) of A. marginale, followed by sequencing to assess diversity of isolates. Microscopic examination of erythrocytes revealed A. marginale inclusion bodies in symptomatic cows. Examination of thin blood smears showed 3.8% of the lactating, clinically asymptomatic, cows to be infected with A. marginale, while nPCR detected 31.0% positive. A. marginale infection was not detected in pregnant heifers by either method. Congenital infection was found in one calf by nPCR. This is the first report of transplacental transmission of A. marginale in Turkey. The MSP4 sequence analyses showed high genetic diversity among the isolates, presenting 97.6-99.6% homology at the amino acid level. The sequences of MSP1a amplicons revealed genetic diversity providing three new tandem repeats.

Fatal congenital anaplasmosis associated with bovine viral diarrhoea virus (BVDV) infection in a crossbred calf.

Clinical disease resulting from the vertical transmission of Anaplasma marginale has only been reported on 5 occasions despite studies demonstrating successful in utero transmission. During the reported experimental induction of congenital anaplasmosis in calves, the outcome was variable but mostly led to inapparent or mild infection. There are previous case reports of fatal congenital anaplasmosis following natural infection. The clinical findings in a 2-day-old calf presented to the Onderstepoort Veterinary Academic Hospital with clinical signs of congenital anaplasmosis, which was unresponsive to treatment, are described. Subsequent post mortem diagnostic tests revealed that this calf was co-infected with bovine viral diarrhoea virus (BVDV). It is postulated that immunosuppression resulting from BVDV infection predisposed to severe, fatal anaplasmosis in this calf.

Transmissäo congênita da anaplasmose bovina / Congenital transmission of anaplasmosis in cattle

A frequência de transmissäo congênita da anaplasmose bovina foi estudada em animais que tiveram infecçäo aguda durante o terceiro trimestre de gestaçäo em vacas portadoras. Onze vacas gestantes, importadas dos Estados Unidos, inoculadas com Anaplasma marginale 60 a 24 dias antes do parto, desenvolveram parasitemia variando de 1,6 a 6,0 por cento, após período de incubaçäo médio de 19,6 dias e nenhuma abortou. Após o parto, dos 11 soros sanguíneos colhidos dos bezerros antes da ingestäo do colostro, quatro (36,0 por cento) apresentaram anticorpos anti A. marginale, detectados pelo teste de DOT-Elisa. Em frigroríficos, foram colhidas 97 amostras de soros fetais provenientes de vacas portadores de diferentes idades, registrando-se apenas duas amostras (2,1 por cento) com anticorpos anti-A. marginale. O mecanismo de transmissäo e sua importância epidemiológica säo discutidos

The persistence of colostral Anaplasma antibodies and incidence of in utero transmission of Anaplasma infections in calves under laboratory conditions.

Twenty-six calves, born from 25 Anaplasma-infected, intact and splenectomized cows, from a herd kept under strict tick-free laboratory conditions, were monitored for the presence of Anaplasma antibodies, using the rapid card agglutination test. Serum was collected at birth, weekly for 12 weeks, and then monthly for approximately 6 months. Specific antibodies passively acquired could be detected in calf sera for an average period of 8 weeks after birth. Calves that remained positive for longer than 12 weeks were suspected of having contracted in utero infections. Infection of the calves was confirmed by splenectomy. It was concluded that 4 calves in Group I contracted in utero infections. Two of the dams were chronically infected, whilst the other 2 underwent acute primary reactions during the 1st and 2nd trimesters of gestation, respectively. Subsequently all calves born from infected cows in this tick-free herd were serologically screened before being splenectomized at an average age of 8 months. Out of 50 cows, 8 in utero infected calves were identified serologically and this finding was confirmed through splenectomy or subinoculation of blood. Both Anaplasma centrale and Anaplasma marginale were carried transplacentally. Splenectomized and intact cows, chronically infected or undergoing primary reactions during the 1st, 2nd or 3rd trimester of gestation, produced infected calves. A 15,6% incidence of in utero transmitted infections were observed amongst 77 calves under these conditions. None of the 13 splenectomized cows, undergoing primary A. centrale infections during gestation, aborted. Clinical signs of disease were not observed in any of the 12 in utero infected calves prior to splenectomy. The implications of these findings are discussed.