can starlings get bird flu

House sparrows, European starlings, and Carneux pigeons were inoculated with 4 influenza A (H5N1) viruses isolated from different avian species. We monitored viral replication, death after infection, and transmission to uninfected contact birds of the same species. Sparrows were susceptible to severe infection; 66%–100% of birds died within 4–7 days. High levels of virus were detected from oropharyngeal and cloacal swabs and in organs of deceased sparrows. Inoculation of starlings caused no deaths, despite high levels of virus shedding evident in oropharyngeal swabs. Least susceptible were pigeons, which had no deaths and very low levels of virus in oropharyngeal and cloacal swabs. Transmission to contact birds did not occur frequently: only A/common magpie/Hong Kong/645/2006 virus was shown to transmit to 1 starling. In summary, recent influenza (H5N1) viruses are pathogenic for small terrestrial bird species but the rate of intraspecies transmission in these hosts is very low.

Highly pathogenic avian influenza viruses of subtype H5N1 were identified in Southeast Asia in 1996 and have spread in recent years across broad regions of Eurasia and Africa. These viruses have shown high lethality in chickens and other poultry species (1–3). Outbreaks of avian influenza, H5N1 subtype and others, have caused massive losses to commercial poultry flocks in recent years (4). Direct transmission of H5N1 subtype from infected poultry is thought to be responsible for virtually all of the human influenza (H5N1) infections since 1997. Because of the effects of influenza (H5N1) on human health and agriculture and its potential to mutate and cause a global pandemic, epidemiologic studies of the viruses’ host range and their means of dispersal are urgently needed (5).

Highly pathogenic poultry isolates from the 1997 and 2001 influenza (H5N1) outbreaks typically cause few disease signs in experimentally infected ducks (6,7). These viruses’ low pathogenicity in waterfowl presumably facilitated efficient carriage to the highly susceptible hosts. Some influenza (H5N1) strains isolated during subsequent outbreaks are highly pathogenic in waterfowl (7,8), and some are shed by infected ducks for prolonged periods (9). Together with the commercial transportation of poultry and poultry products, migratory waterfowl are likely to have played a role in the wide dispersal of highly pathogenic influenza (H5N1) viruses.

Land-based wild bird populations may also be vulnerable to lethal influenza (H5N1) infection and could contribute to the spread and interspecies transmission of the viruses. Small terrestrial birds are potentially important hosts in influenza (H5N1) ecology because many of them intermingle freely with wild and domestic populations of waterfowl and poultry. However, data describing their susceptibility to influenza virus (H5N1) infection or their potential to transmit the viruses are limited.

A study investigating the host range of A/chicken/Hong Kong/220/97 showed that it causes lethal infection in budgerigars and finches (10). In contrast, the same virus replicated poorly in sparrows, causing no deaths, and, when pigeons were inoculated, replication of this virus was not evident. A more recent chicken influenza (H5N1) isolate (A/chicken/Yamaguchi/7/2004), highly lethal to chickens and quail, also replicates extensively and causes high mortality rates in budgerigars (11). Since 2002, influenza (H5N1) viruses have been isolated from dead birds of several wild terrestrial species, including magpie, tree sparrow, pigeon, and large-billed crow (8,12,13). Viruses of a novel influenza (H5N1) genotype were isolated during a survey of live tree sparrows (Passer montanus); these isolates were highly pathogenic to chickens (14). Together, these reports indicate that some small, land-based bird species are susceptible to infection, sometimes fatal, with highly pathogenic influenza (H5N1) viruses.

We inoculated sparrows, starlings, and pigeons with several recent highly pathogenic influenza (H5N1) viruses isolated from a variety of avian hosts. The primary aims of the study were to test the susceptibility of different species to infection, investigate the duration and routes of viral shedding from the birds, and assess the possibility of intraspecies viral transmission in these hosts.

Four influenza A (H5N1) virus strains were studied, 2 from previously known susceptible hosts (duck and quail) and 2 from previously unknown hosts (common magpie and Japanese white-eye). The A/duck/Thailand/144/2005 (A/DK/TH/144/05) and A/quail/Thailand/551/2005 (A/Q/TH/551/05) viruses were isolated from western Thailand and tested for their pathogenicity in ducks (15). The other 2 viruses, A/common magpie/Hong Kong/645/2006 (A/CM/HK/645/06) and A/Japanese white-eye/Hong Kong/1038/2006 (A/JW/HK/1038/06) were provided to us by K.C. Dyrting and C.W.W. Wong (Agriculture, Fisheries and Conservation Department in Hong Kong). They were isolated from dead wild birds collected in January and February 2006 during the heightened Hong Kong territory-wide avian influenza surveillance of dead wild birds that started in October 2005.Upon arrival at St Jude Children’s Research Hospital, the viruses were propagated in 10-day-old embryonated chicken eggs.

Wild house sparrows (Passer domesticus) and European starlings (Sturnus vulgaris), both members of the order Passeriformes, were captured. Six-week-old white Carneux pigeons (Colomba spp.), members of the order Columbiformes, were purchased from Palmetto Pigeon Plant (Sumter, SC, USA) and Double T farms (Glenwood, IA, USA). Birds were housed in cages in the St Jude Children’s Research Hospital Animal Biosafety Level 3+ containment facility, food and water were provided ad libitum, and general care was provided as required by the Institutional Animal Care and Use Committee. Before inoculation with virus, oropharyngeal and cloacal swabs were collected to exclude preexisting influenza A virus infection.

Three sparrows and pigeons were inoculated intranasally with 1 million 50% egg infectious doses (EID50) in 50 ?L or 500 ?L phosphate-buffered saline, respectively, for each virus. Because of their limited availability, starlings were inoculated with 3 viruses (1 million EID50 in 150 ?L), and group sizes were reduced (1 bird for A/DK/TH/144/05, 3 birds for A/CM/HK/645/06, and 2 birds for A/JW/HK/1038/06). One day after inoculation, uninfected contact birds, at a ratio of 1:1 for sparrows and starlings or 2:3 for pigeons, were housed together with inoculated animals to study intraspecies transmission. Birds were monitored daily for death and illness for a 14-day period. After inoculation, oropharyngeal and cloacal swabs were collected on days 2, 4, 6, 8, and 11 for sparrows and starlings and days 3, 5, and 7 for pigeons. Influenza virus was detected by using 10-day-old embryonated chicken eggs as previously described (7). EID50 virus titers were determined in positive swabs by using the method of Reed and Muench (15). The lower limit of quantitation of the assay is 100.75 EID50/mL, and average virus titers in organs and swabs were calculated by using the log10 value of each sample.

Fourteen days after inoculation with virus, serum specimens were collected from inoculated and contact birds, and hemagglutination-inhibition (HI) titers were determined according to standard methods (16,17) by using chicken erythrocytes and 4 hemagglutinating units of virus. An HI titer >10 suggested a recent influenza virus infection; an HI titer <10 was considered negative.

Common songbirds in Hong Kong “have been dropping dead out of the sky” over the last two winters, according to Robert Webster, an infectious diseases specialist at St Jude Children’s Research Hospital in Memphis, Tenn. Some of those birds died from avian influenza. Webster and his associates were interested in learning if birds could be a factor in the virus’s spread.

Scientists discovered in a lab experiment that starlings infected with four different avian influenza strains breathed and excreted copious amounts of virus. The first instance of starling-to-starling transmission has been documented, wherein an uninfected starling acquired the bug from its cagemates.

According to Boyce, the research “adds another piece of the puzzle.” However, there isn’t much proof that these common songbirds will serve as a major virus source for the other animals they come into contact with. ”.

Webster’s team discovered in additional tests that common pigeons and house sparrows did not transmit the virus to other members of their species. Sparrows were poor long-term carriers because they spread a lot of the virus but died 4–6 days after infection. Pigeons infected with the virus did not exhibit symptoms and only exhaled and feces trace amounts of the virus, suggesting that they would also be a poor reservoir for bird flu.

Millions of chickens have been culled as a result of H5N1 avian influenza virus outbreaks that have occurred in Asia, Europe, and Africa since 1996. Experts believe that H5N1, which differs genetically from influenza viruses that spread throughout the United States every winter, is naturally found in ducks and other waterfowl.

Infection of Different Bird Species with Influenza (H5N1) Virus

It was discovered that four distinct influenza A (H5N1) viruses could infect and sicken house sparrows, European starlings, and white Carneux pigeons. Depending on the virus that was vaccinated, %20sparrow%20infection%20caused%20death%20in%2066%%E2%80%93100%%20of%20the%20infected%20animals%20(%20) The average time to death varied from 4. 2 days for A/DK/TH/144/05 to 6. 3 days for A/Q/TH/551/05 virus (data not shown). The brain and lung tissues of the deceased sparrows had high viral loads (, panel C) Conversely, following their vaccination with these viruses, none of the pigeons or starlings perished.

All of the tested viruses were found to have infected the sparrows and starlings, according to a re-isolation of the virus from oropharyngeal and cloacal swabs taken at different times following inoculation. On the other hand, there was significant variation in the frequency of virus re-isolation from inoculated pigeons. A/CM/HK/645/06, one of the four H5N1 subtypes, showed the widest host range, infecting all of the inoculated pigeons in addition to sparrows and starlings. The virus known as A/DK/TH/144/05%20, which resulted in 20100% mortality in sparrows within 204% 2 days after inoculation, was not re-isolated from inoculated pigeons.

The analysis of the virus titer in the swabs revealed that the quantity of virus secreted by sparrows and starlings in oropharyngeal swabs was comparable. But compared to cloacal swabs from infected starlings, the virus titers in the sparrows’ samples were higher. The similarity in oral shedding between sparrows and starlings was verified by comparing the peak virus titers in oropharyngeal swabs. On the other hand, starling cloacal swabs showed lower peak virus titers (, panels A and B). The average oropharyngeal and cloacal shedding on days 3 and 5() and the peak virus titers in oropharyngeal and cloacal swabs (, panels A and B) indicate that the 2005–2006 influenza (H5N1) viruses replicated relatively poorly in pigeons.

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