Investigation of A Multi-Pathogen Outbreak in Recently Transported Holstein Friesian Cattle, Andhra Pradesh, India

Abstract

Background: Long-distance transport and adaptation to new management conditions can predispose dairy cattle to infectious disease outbreaks, particularly in high-yielding exotic breeds. Aim: This investigation aimed to characterise a severe outbreak in recently transported Holstein Friesian cattle in Andhra Pradesh, India, and to assess the possible contributions of infectious agents, transport stress, management deficiencies and breed-associated susceptibility. Method: A commercial dairy farm with 100 Holstein Friesian and 50 Gir cattle transported from Haryana was investigated after high mortality occurred among Holstein Friesian cattle. Twenty clinically affected animals were examined using clinical assessment, faecal examination, Giemsa-stained blood smears, ELISA, PCR and histopathology. Serum and whole-blood samples were tested for selected bacterial, viral, parasitic and haemoprotozoan infections. Results: Within 3–4 weeks of arrival, 55 Holstein Friesian cattle died, whereas no clinical illness or mortality was observed among Gir cattle on the same farm. Faecal examination detected Balantidium spp. in all sampled animals (20/20), and microfilariae were identified in 3/20 blood smears. ELISA detected antibodies against Brucella spp. (4/20), BoHV-1 (2/20) and Chlamydia spp. (5/20), while Leptospira spp. was not detected. PCR identified Theileria annulata (2/20), BoHV-1 (3/20) and MCF virus (4/20), with two animals concurrently positive for these pathogens. Histopathology showed multisystem lesions involving major organs. Conclusion: The outbreak was consistent with a multifactorial disease event associated with transport stress, inadequate management, vector exposure and concurrent infections. The findings emphasise quarantine, pre-purchase screening, biosecurity, vector control and breed adaptability in tropical dairy systems.