Seroprevalence of antibodies to astrovirus in chickens in Grenada, West Indies

An Insight into the Molecular Characteristics and Associated Pathology of Chicken Astroviruses

The chicken astrovirus (CAstV) is a ubiquitous enteric RNA virus that has been associated mainly with conditions, such as the runting-stunting syndrome, severe kidney disease, visceral gout, and white chick syndrome, in broiler-type chickens worldwide. Sequence analysis of the capsid genes’ amino acids of the strains involved in these conditions reveals a genetic relationship and diversity between and within the CAstV genogroups and subgroups based on phylogenetic analysis, genetic distance (p-dist), and pathogenicity. While the two genogroups (A and B) are demarcated phylogenetically, their pairwise amino acid sequence identity is 39% to 42% at a p-dist of 0.59 to 0.62. Group-A consists of three subgroups (Ai, Aii, and Aiii) with an inter- and intra-subgroup amino acid identity of 78% to 82% and 92% to 100%, respectively, and a p-dist of 0.18 to 0.22. On the other hand, the six subgroups (Bi, Bii, Biii, Biv, Bv, and Bvi) in Group-B, with a p-dist of 0.07 to 0.18, have an inter- and intra-subgroup amino acid identity of 82% to 93% and 93% to 100%, respectively. However, these groupings have little to no effect on determining the type of CAstV-associated pathology in chickens.

A Cross Sectional Survey of Chicken Astroviruses Antibody in Broiler and Sonali (Cross-Bred) Chickens in Selected Areas in Bangladesh

Chicken astroviruses (CAstV) are enteric viruses of poultry causing gastroenteritis, malabsorption, gout and white chick disease commonly known as runting-stunting syndrome (RSS). It can affect the wide range of poultry birds, especially chicken, turkey and duck worldwide. To our best knowledge there is no published report on presence of antibodies against CAstV in Bangladesh. Therefore, the study aimed to detect the presence of CAstV antibodies in broilers and sonali chickens (a cross-bread) in Bangladesh through a cross-sectional survey. A total of 454 blood samples from 66 flocks of broiler (n=343) and sonali chickens (n=111) of different ages were obtained during 2017 from four districts. The birds were healthy but were not vaccinated against CAstV. The samples were tested for specific antibodies against CAstV Group B by using commercially available ELISA kit. Overall, 16.74% (76/454) samples and 34.84% (23/66) flocks were positive for CAstV antibodies. The seroprevalence of CAstV was significantly (p=0.001) higher in sonali chickens (36.96%) than broiler (10.20%), while it was significantly higher (p=0.001) in birds of Bogura district (36.94%) than the other three districts. Regarding the age groups, seroprevalence was insignificantly (p=0.192) higher in sonali chicken before laying age (45%) than during laying age (27.45%). Regarding the seasons, CAstV infection was prevalent significantly (p=0.001) higher in winter season. Thus, the present study indicated the presence of CAstV in poultry in Bangladesh, so further studies are required to find out the magnitude of the problem in the country.

Infections and pathology of free-roaming backyard chickens on St. Kitts, West Indies

Free-roaming chickens on Caribbean islands are important sentinels for local avian diseases and those introduced by birds migrating through the Americas. We studied 81 apparently healthy unvaccinated free-roaming chickens from 9 parishes on St. Kitts, an eastern Caribbean island. Using commercial ELISAs, no chickens had antibodies against avian influenza virus, West Nile virus, or Salmonella Enteritidis, although seropositivity was high to infectious bursal disease virus (86%), infectious bronchitis virus (84%), Mycoplasma (37%), and avian avulavirus 1 (Newcastle disease virus, 31%). Examination of small and large intestinal contents revealed cestodes in 79% and nematodes in 75% of the chickens. Although ectoparasites and endoparasites were common (74% and 79%, respectively), only a few chickens had lesions at postmortem examination, mainly intestinal serosal nodules (12%) and feather loss (6%). Histologic examination of 18 organs from each bird revealed lesions in high percentages of organs, mainly the liver (86%), lung (75%), spleen (60%), small intestine (56%), skin (42%), and kidney (40%). Lesions included degenerative, reactive, inflammatory, and neoplastic, and were not correlated with the serologic status of the chickens except in one case of infectious bursal disease. Microscopically, Paratanaisia bragai was seen in the kidneys of 3 chickens and intestinal coccidiasis in 1 chicken. Pulmonary silicate aggregates were common, were present in intestinal serosal nodules, and were suggestive of environmental exposure.