Influence of aquatic invertebrates on the persistence and infectivity of Avian Flu

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Little is known about the influence of aquatic invertebrates on the persistence and infectivity of avian influenza virus (AI) in aquatic environments. LIDE conducted laboratory experiments to investigate the ability of an aquatic filter-feeding invertebrate (eaten in large quantities by some ducks) to accumulate and potentially transmit infective virus to waterfowl from AI-contaminated water.

Understanding the ecology and transmission of avian influenza virus (AI) in the environment among its natural hosts is important for preventing infections in poultry and people. Avian influenza can be divided into two basic groups: highly deadly strains and low-pathogenicity strains (LPAI). LPAI causes mild illness in poultry (including a decline in egg production) and LPAI strains are common in waterfowl where the virus is thought to be transmitted through water contaminated with feces from infected birds.

Transmission efficiency of AI likely depends on how long the virus can survive in water, however, little is known about the influence of aquatic invertebrates on the persistence and infectivity of AI in aquatic environments. To investigate, LIDE conducted laboratory experiments on the ability of an aquatic filter-feeding invertebrate, Daphnia magna (common water flea), to accumulate virus from LPAI-contaminated water. Water fleas are filter feeders, and AI can potentially accumulate in their bodies through feeding. Since water fleas are eaten in large quantities by some ducks, they could potentially provide a shortcut in the transmission route from LPAI-contaminated water to ingestion by waterfowl.

LIDE placed live Daphnia in test tubes with LPAI-contaminated water. Daphnia tissue and the surrounding water were sampled using reverse transcription-quantitative PCR (RT-qPCR) at 3-min to 2-hour intervals for up to 16 hours following dosing. LIDE's experiments showed Daphnia quickly accumulated AI in its body during feeding, and correspondingly, the AI concentration in the water decreased; the Daphnia were, in effect, clearing the water of virus, which would benefit waterfowl by reducing the likelihood of infection. When the ingested virus was isolated from the flea's body tissue, the virus was no longer infectious, suggesting Daphnia's feeding activity killed the virus.

However, LIDE cannot completely dismiss the idea that Daphnia does not transmit infectious AI; at shorter time scales, infective AI might have been present in Daphnia tissue. More sensitive methods might also have detected infective virus inside Daphnia.

 

Read more about this study:

Meixell BW, Borchardt MA, Spencer SK. 2013. Accumulation and inactivation of avian influenza virus by the filter-feeding invertebrate Daphnia magna. Appl. Env. Micro. 79:7249-7255.