Cross-species transmission of poultry pathogens in backyard farms: ducks as carriers of chicken viruses.

In backyard farms of Lao People's Democratic Republic, mixed-species rearing of poultry is a breeding-ground for cross-species transmission. Here, the epidemiology of viruses circulating among backyard poultry in Vientiane Province was assessed to guide future control strategies. Oral/tracheal and cloacal swabs, collected from 605 poultry (308 ducks, 297 chickens) between 2011 and 2015, were screened by PCR for Newcastle disease virus (NDV), coronavirus (CoV) and chicken anaemia virus (CAV). Chicken sera were screened for anti-NDV antibodies by ELISA. Statistical and phylogenetic analyses revealed transmission patterns and relationships. Closely related strains co-circulated in chickens and ducks. While CoV RNA was detected in oral/tracheal swabs of 9.3% of the chickens and 2.4% of the ducks, rates were higher in faecal swabs of both species (27.3% and 48.2%). RNA of infectious bronchitis virus (IBV) and duck CoV was found in faecal swabs of chickens (19.7% and 7.1%) and ducks (4.1% and 44.1%). Moreover, DNA of the generally chicken-specific CAV was detected in oral/tracheal swabs of chickens (18.1%) and, sporadically, of ducks (2.4%). Despite serological evidence of NDV circulation or vaccination (86.9%), NDV RNA was not detected. We found a high prevalence and indication for cross-species transmission of different CoV strains in backyard poultry. Interestingly, ducks served as biological, or at least mechanical, carriers of viral strains closely related not only to IBV, but also to CAV. Bird containment and poultry species separation could be first steps to avoid cross-species transmission and emergence of novel strains with broad host range and enhanced pathogenicity. RESEARCH HIGHLIGHTS High rates of avian viruses were detected by PCR in backyard poultry from Lao PDR. Diverse coronavirus and chicken anemia virus strains co-circulated. Phylogenetic analyses suggested virus transmission between chickens and ducks. Serological evidence of Newcastle disease was found, but viral RNA was not detected.

High circulation of Hepatitis E virus in pigs and professionals exposed to pigs in Laos.

Epidemiological characteristics of hepatitis E Virus (HEV) differ due to the vast spatial heterogeneity in sanitation status, dietary habits and extent of exposure to animals. Although HEV infections are mostly asymptomatic, prognosis is poor for patients with compromised immune systems or pre-existing liver disease and during pregnancy. In developing countries, low hygienic standards and close human-animal interactions at farms and slaughterhouses likely favour zoonotic transmission of the virus. In this cross-sectional study from Lao People's Democratic Republic, anti-HEV IgG was detected by ELISA in 54.0% (136/252) of slaughter pigs, in 41.0% (57/139) of professionals exposed to pigs and in 18.1% of the nonrisk controls (38/210). We show that people occupationally exposed to pigs are at higher risk of infection (p < 0.001). In particular, contact to young piglets as compared to contact to the older slaughter pigs was a major risk factor (p = 0.011). Besides, consumption of bottled water significantly reduced the risk of infection (p = 0.018). In conclusion, we show that in Lao PDR, the high endemicity of HEV, the inadequate implementation of hygiene measures and the limited access to safe water jeopardize the health of professionals exposed to pigs.

Evidence of increased Hepatitis E virus exposure in Lao villagers with contact to ruminants.

Although pigs are the main reservoir, ruminants have also been shown to be susceptible to hepatitis E virus (HEV). We investigated zoonotic transmission of HEV in rural settings of Lao People's Democratic Republic (Lao PDR) where humans are in close contacts with ruminants and where pigs are rare. Villagers with (n = 171, risk group) and without (n = 155, control group) cattle were recruited in seven villages in Vientiane Capital. Owners of pigs were excluded. Blood, as well as information on socio-demographics, animal contact, dietary habits and awareness of zoonoses were collected to assess risk factors. Blood and rectal swabs were collected from cattle (n = 173) and other ruminants (27 goat, 5 buffaloes) to measure anti-HEV antibody and virus prevalence. A similar anti-HEV antibody seroprevalence was found in cattle (6.8%) and other ruminants (8%). HEV RNA was detected in none of the animal rectal swabs and human sera. Anti-HEV IgG seroprevalence was higher in cattle farmers than in the control group (59.1% vs. 43.9%, p = 0.008) and increased significantly with age. Other risk factors included male gender, close contact with cattle and consumption of undercooked meat. We find that HEV is highly endemic in rural Laos and provide first evidence that HEV circulates in free-roaming ruminants with open access to village water sources. Despite some awareness about hygiene, villagers are likely constantly exposed to zoonotic diseases by dietary and lifestyle habits. Cattle farmers had a higher risk of HEV infection than other villagers. Our study highlights the need to raise the awareness of the rural population about water- and food-borne pathogens, and about the role of cattle as a possible source of infection. The knowledge gained on local risk factors and husbandry conditions should guide future awareness raising campaigns and promote appropriate hygienic measures including handwashing and the consumption of safe food and water.