PATHOLOGICAL AND MOLECULAR INVESTIGATION OF HEPATOMEGALY AND SPLENOMEGALY SYNDROME IN POULTRY IN CHATTOGRAM

Abstract

Enlarged liver and spleen are notable pathological lesions in poultry indicative of many infectious diseases that leads to economic losses due to high mortality rates and reduced egg production. Various bacteria, viruses, and infectious agents are associated with these notable lesions in the poultry. In this study, we conducted a cross-sectional study using enlarged liver and spleen samples from 35 different dead chickens (15 layers and 20 broilers). These samples were collected after postmortem examination from the dead birds brought to the department of Pathology and Parasitology at Chattogram Veterinary and Animal Sciences University (CVASU), by different poultry farm owners in Chattogram district for diagnosis and treatment purposes. Among those samples 4 different layer birds had whitish nodular lesions in the liver and spleen and tentatively diagnosed as Marek’s disease (MD) or Lymphoid leukosis (LL). However, in other cases congestive lesions were markedly observed in liver and spleen and were diagnosed as E. coli, Salmonella or other viral infections. There were no perihepatitis or hemorrhage in abdominal cavity in any cases. After necropsy, swab samples from liver and spleen were initially inoculated into selenite cystine broth and blood agar, and subsequently streaked onto EMB and XLD agar for the isolation and identification of bacterial colony. A part of the samples were also preserved in 10% buffered formalin for histopathological examinations, and in -200C for molecular work. After bacteriological culture 17 (48.5%) samples showed predominantly positive results for E.coli on EMB agar, while no Salmonella sp were positive on XLD agar, based on colony characteristics. For molecular confirmation DNA was extracted from those 4-layer bird samples (liver and spleen) that were suspected MD/LL, and PCR was done initially using ICP4 gene primers for MD virus. Finally, it’s found that 3 samples were amplified for ICP4 gene and confirmed to be Marek's disease. But due to limitations RNA couldn’t be extracted and RT-PCR couldn’t be done to check another sample with nodular lesion which might be LL or due to other RNA viruses. Furthermore, the liver and spleen samples with nodular lesions and some other samples were investigated for histopathological lesions which reveals notable findings include- severe congestion and hemorrhages, neoplastic foci with the accumulation of pleomorphic cells specially lymphoblast, various sized lymphocyte, and macrophages in the liver. In spleen, various sized lymphocytes along with extended white pulp also found which is composed of reticular cells indicative xii for extensive inflammatory reaction. In conclusion, molecular diagnosis is necessary for hepatomegaly and splenomegaly along with the histopathological examinations that is associated with any lymphoproliferative lesions.