Epizootiology of avian influenza: effect of season on incidence in sentinel ducks and domestic turkeys in Minnesota

Abstract

Sentinel ducks and domestic turkey flocks were monitored for influenza infection during a 4-year period. The onset of infection among ducks was similar each year, occurring in late July or early August. Influenza in turkeys was also shown to be seasonal, but the usual onset was 6 to 8 weeks after the detection of influenza in sentinel ducks. Possible explanations for the delayed infection in turkeys are (i) increased waterfowl activity associated with fledging and congregating in late summer and early fall; (ii) vectors transmitting virus from the waterfowl habitat to poultry farms; (iii) cooler environmental temperature, allowing prolonged virus viability; (iv) cooler surface water temperature, allowing prolonged virus viability; (v) groundwater contamination from contaminated surface water; and (vi) virus adaptation in domestic turkeys before infection is detected. We conclude that ducks are not only a natural reservoir of influenza but also have a seasonal infection that appears to be related to seasonal influenza outbreaks in domestic turkeys in Minnesota. However, only some influenza A virus isolates circulating among waterfowl at any given time appear capable of causing detectable infection in turkeys. It is speculated that the seasonal infection in migratory waterfowl may also be related to seasonal influenza infections in other species including humans.

Low‐pathogenic notifiable avian influenza serosurveillance and the risk of infection in poultry – a critical review of the European Union active surveillance programme (2005–2007)

“…The higher risk observed in waterfowl might be related to the species relatedness with migratory wild waterfowl, their long lifespan and the fact that these PTs are mainly kept outdoors which is associated with a higher risk of exposure to AIVs from the environment and wild fauna. 19,33,34 Commercial layers were the most targeted PT. This PT was targeted assuming a higher risk due to their lifespan and their production characteristics (e.g.…”

The calendar of epidemics: Seasonal cycles of infectious diseases

“…Winter in both humans and poultry (in Asia) [9,10] Bacterial Pneumonia Acute c, d, and e Peaks in midwinter (in the US); it is associated with influenza [11] Brucellosis Acute b Spring and summer in wildlife and livestock; the timing relates to the birthing season; peaks in the summer in humans [12] Buruli ulcer Chronic c Varies by location; some studies have not observed seasonality [13] Chagas disease Acute and chronic a Peaks in spring and summer in countries with distinct seasons [14] Chickenpox acute f Peak in spring in the Northern and Southern Hemisphere [15] Chikungunya Acute a Rainy season when vector density peaks. [16] Cholera Acute c, d, and g Seasonality is stronger in countries further from the equator; outbreaks generally occur in warm months [17] Crimean-Congo hemorrhagic fever Acute a Seropositivity in livestock correlates with seasonal changes in tick parasitism; human cases correlate with livestock seropositivity [18] Cryptosporidium Acute c Increased risk of cryptosporidium associated with high ambient temperature and high rainfall [19] Cutaneous leishmaniasis Acute and chronic a and b Strong seasonal variation with elevated incidence from October to March (in Tunisia).…”

Surveillance for highly pathogenic avian influenza in wild birds in the USA

“…Waterfowl, exhibition game fowl and poultry flocks reared on backyard premises have been used as sentinels for active surveillance for avian diseases of interest to the commercial poultry industry and regulatory agencies (McBride et al 1991;Johnson et al 2004). Sentinel ducks have been used effectively to determine the presence of AIV and timing of infection associated with the arrival of wild migratory waterfowl in wetland habitats (Turek et al 1984;Sinnecker et al 1982a,b;Halvorson et al 1983;Halvorson et al 1985;Kelleher et al 1985).…”

“…Major advantages of sentinel bird surveillance include the previous success of such systems to effectively detect AIV (Halvorson et al 1983;Halvorson et al 1985) and the applicability in areas in which other methods cannot be used (e.g. urban areas).…”