Scavenging Ducks and Transmission of Highly Pathogenic Avian Influenza, Java, Indonesia - EID - CDC Volume 16, Number 8–August 2010

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Volume 16, Number 8–August 2010
Research
Scavenging Ducks and Transmission of Highly Pathogenic Avian Influenza, Java, Indonesia
Joerg Henning , Hendra Wibawa, John Morton, Tri Bhakti Usman, Akhmad Junaidi, and Joanne Meers
The University of Queensland, Brisbane, Queensland, Australia (J. Henning, J. Morton, J. Meers); Australian Animal Health Laboratory, Geelong, Victoria, Australia (H. Wibawa); and Disease Investigation Centre, Wates, Indonesia (T.B. Usman, A. Junaidi)

Suggested citation for this article

Abstract
In Java, Indonesia, during March 2007–March 2008, 96 farms with scavenging ducks that were not vaccinated against highly pathogenic avian influenza (HPAI) were monitored bimonthly. Bird-level (prevalence among individual birds) H5 seroprevalence was 2.6% for ducks and 0.5% for chickens in contact with ducks. At least 1 seropositive bird was detected during 19.5% and 2.0% of duck- and chicken-flock visits, respectively. Duck flocks were 12.4× more likely than chicken flocks to have seropositive birds. During 21.4% of farm visits, ³1 sampled duck was H5 seropositive when all sampled in-contact chickens were seronegative. Subtype H5 virus was detected during 2.5% of duck-flock visits and 1.5% of chicken-flock visits. When deaths from HPAI infection occurred, H5 virus shedding occurred in apparently healthy birds on 68.8% of farms. Of 180 poultry deaths investigated, 43.9% were attributed to H5 virus. These longitudinal study results indicate that ducks are a source of infection for chickens and, potentially, for humans.

Since 1997, when highly pathogenic avian influenza (HPAI) subtype H5N1 outbreaks occurred in poultry in Hong Kong, People's Republic of China (1–2), the virus has caused epidemics in Asia, Europe, and Africa (3). In Indonesia, the first HPAI (H5N1) virus infections in poultry were officially announced in early 2004 (4); human cases have been reported since mid-2005 (5). Although extensive HPAI control efforts helped reduce the frequency of outbreaks in poultry (6), by 2009, subtype H5N1 virus had been detected in 31 of Indonesia's 33 provinces (7). In 2009, Indonesia had the highest incidence worldwide of human infections and deaths (8).

Waterfowl are the natural reservoir of avian influenza viruses (9), and experimental research indicates that ducks may play a role in the maintenance of HPAI (H5N1) viruses. Infected ducks may exhibit no clinical signs yet can excrete high concentrations of virus that are pathogenic to other poultry species (10–13). Possible risk factors for HPAI spread in Indonesia include duck movements, contacts between ducks and other poultry and animal species, poor poultry husbandry, inadequate handling of sick and dead ducks by flock owners, and poor awareness of control strategies among poultry farmers (14). However, no analytical study assessing risk factors for HPAI infection has been conducted in Indonesia.

In 2005, Indonesia's duck population was ≈34.3 million, of which 40% were on the island of Java, mainly on smallholder farms, i.e., backyard and small commercial farms (14). As in many other Asian countries, domestic ducks on smallholder farms in Indonesia are allowed to scavenge freely during the day around houses, in the villages, or in rice paddies; duck owners supply little or no feed (15). To assess the hypothesis that ducks contribute to the maintenance and transmission of avian influenza (H5N1) viruses, we conducted a longitudinal investigation describing temporal patterns of antibodies against HPAI (H5) and virus prevalence in unvaccinated scavenging ducks and chickens that have contact with these ducks (in-contact chickens) in Java, Indonesia.

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Suggested Citation for this Article
Henning J, Wibawa H, Morton J, Usman TB, Junaidi A, Meers J. Scavenging ducks and transmission of highly pathogenic avian influenza, Indonesia. Emerg Infect Dis [serial on the Internet]. 2010 Aug [date cited]. http://www.cdc.gov/EID/content/16/8/1244.htm

DOI: 10.3201/eid1608.091540