Exposure to a low pathogenic A/H7N2 virus in chickens protects against highly pathogenic A/H7N1 virus but not against subsequent infection with A/H5N1.

Recent evidences have demonstrated that the presence of low pathogenic avian influenza viruses (LPAIV) may play an important role in host ecology and transmission of avian influenza viruses (AIV). While some authors have clearly demonstrated that LPAIV can mutate to render highly pathogenic avian influenza viruses (HPAIV), others have shown that their presence could provide the host with enough immunological memory to resist re-infections with HPAIV. In order to experimentally study the role of pre-existing host immunity, chickens previously infected with H7N2 LPAIV were subsequently challenged with H7N1 HPAIV. Pre-infection of chickens with H7N2 LAPIV conferred protection against the lethal challenge with H7N1 HPAIV, dramatically reducing the viral shedding, the clinical signs and the pathological outcome. Correlating with the protection afforded, sera from chickens primed with H7N2 LPAIV reacted with the H7-AIV subtype in hemagglutination inhibition assay and specifically with the N2-neuraminidase antigen. Conversely, subsequent exposure to H5N1 HPAIV resulted in a two days-delay on the onset of disease but all chickens died by 7 days post-challenge. Lack of protection correlated with the absence of H5-hemagglutining inhibitory antibodies prior to H5N1 HPAIV challenge. Our data suggest that in naturally occurring outbreaks of HPAIV, birds with pre-existing immunity to LPAIV could survive lethal infections with HA-homologous HPAIV but not subsequent re-infections with HA-heterologous HPAIV. These results could be useful to better understand the dynamics of AIV in chickens and might help in future vaccine formulations.

Intestinal excretion of a wild bird-origin H3N8 low pathogenic avian influenza virus in mallards (Anas Platyrhynchos).

Mallards (Anas platyrhynchos) and other dabbling ducks in the genus Anas are an important component of the wild bird reservoir for avian influenza (AI) virus; these viruses are maintained in migratory duck populations through a fecal-oral transmission route. We provide a detailed characterization of intestinal viral shedding in Mallards infected with a wild bird-origin low pathogenic (LP) AI virus. Five of eight, 1-mo-old Mallards inoculated with a high dose of an H3N8 LP AI virus became infected as determined by reisolation and seroconversion. Infected birds excreted high concentrations of virus for up to 14 days postinoculation (DPI) without exhibiting overt clinical signs of disease. The pattern of viral shedding was relatively consistent between individual birds, with peak shedding on 2-3 DPI and a progressive decline over the remainder of infection. Detection of viral shedding varied depending on sample type (excrement sample or cloacal swab) and diagnostic test (virus isolation or real-time quantitative reverse transcription polymerase chain reaction). Our data provide detailed insights into the intestinal excretion of an H3N8 LP AI virus in Mallards and the performance of diagnostic assays commonly used in wild bird surveillance. Such information is valuable for estimating potential risks for spillover of LP AI viruses from Mallards to domestic animals, developing accurate transmission models for Mallard populations and facilitating the interpretation and comparison of surveillance results from different studies.

Experimental West Nile virus infection in Gyr-Saker hybrid falcons.

West Nile disease (WND) has become a major public and veterinary health concern since the appearance of West Nile virus (WNV) in New York in 1999. The following panzootic spread in the U.S. and the recent WNV outbreaks in Europe and the Mediterranean Basin have increased interest in WND. Despite considerable investigation of WNV infection in birds, the effects of WNV on avian populations are still largely unknown. In Europe, raptors have been found to be particularly susceptible to WNV infection, but studies in birds of prey are lacking. To our knowledge, the present study is the first to report an experimental infection with WNV in Gyr-Saker hybrid falcons. We show that 10-week-old captive-reared Gyr-Saker (Falco rusticolus × Falco cherrug) hybrid falcons are susceptible to WNV infection. Neither morbidity nor mortality was observed after subcutaneous WNV inoculation with mixed extracts of non-infected mosquito salivary glands. Both the macroscopic and microscopic lesions observed were similar to those previously reported in naturally and experimentally infected North American raptors. The results obtained in the present study demonstrate that although Gyr-Saker hybrid falcons do not seem to be a good reservoir for WNV transmission via mosquito, they can become infected with WNV, develop viremia and antibodies, and are able to shed the virus.

Clinical and pathologic characteristics of T-cell lymphoma with a leukemic phase in a raccoon dog (Nyctereutes procyonoides).

A 7.5-year-old raccoon dog (Nyctereutes procyonoides) from the Henry Doorly Zoo (Omaha, Nebraska) presented to the veterinary hospital for lethargy and weight loss. On physical examination, splenomegaly and hepatomegaly were noted on palpation and were confirmed by radiographic evaluation. Radiography also demonstrated a mass in the cranial mediastinum. A complete blood cell count revealed marked leukocytosis (115,200 cells/µl), with a predominance of lymphoid cells. The animal was euthanized due to a poor prognosis. Necropsy revealed splenomegaly, hepatomegaly, and a large multiloculated mass in the cranial mediastinum. The histologic and immunohistochemical diagnosis was multicentric T-cell lymphoma with a leukemic phase.

Variation in viral shedding patterns between different wild bird species infected experimentally with low-pathogenicity avian influenza viruses that originated from wild birds.

The prevalence of infection with avian influenza (AI) virus varies significantly between taxonomic Orders and even between species within the same Order. The current understanding of AI infection and virus shedding parameters in wild birds is limited and largely based on trials conducted in mallards (Anas platyrhynchos). The objective of the present study was to provide experimental data to examine species-related differences in susceptibility and viral shedding associated with wild bird-origin low-pathogenicity avian influenza (LPAI) viruses in multiple duck species and gulls. Thus mallards, redheads (Aythya americana), wood ducks (Aix sponsa), and laughing gulls (Leucophaeus atricilla) were inoculated experimentally with three wild mallard-origin LPAI viruses representing multiple subtypes. Variation in susceptibility and patterns of viral shedding associated with LPAI virus infection was evident between the duck and gull species. Consistent with the literature, mallards excreted virus predominantly via the gastrointestinal tract. In wood ducks, redheads, and laughing gulls, AI virus was detected more often in oropharyngeal swabs than cloacal swabs. The results of this study suggest that LPAI shedding varies between taxonomically related avian species. Such differences may be important for understanding the potential role of individual species in the transmission and maintenance of LPAI viruses and may have implications for improving sampling strategies for LPAI detection. Additional comparative studies, which include LPAI viruses originating from non-mallard species, are necessary to further characterize these infections in wild avian species other than mallards and provide a mechanism to explain these differences in viral excretion.

Homo- and heterosubtypic low pathogenic avian influenza exposure on H5N1 highly pathogenic avian influenza virus infection in wood ducks (Aix sponsa).

Wild birds in the Orders Anseriformes and Charadriiformes are the natural reservoirs for avian influenza (AI) viruses. Although they are often infected with multiple AI viruses, the significance and extent of acquired immunity in these populations is not understood. Pre-existing immunity to AI virus has been shown to modulate the outcome of a highly pathogenic avian influenza (HPAI) virus infection in multiple domestic avian species, but few studies have addressed this effect in wild birds. In this study, the effect of pre-exposure to homosubtypic (homologous hemagglutinin) and heterosubtypic (heterologous hemagglutinin) low pathogenic avian influenza (LPAI) viruses on the outcome of a H5N1 HPAI virus infection in wood ducks (Aix sponsa) was evaluated. Pre-exposure of wood ducks to different LPAI viruses did not prevent infection with H5N1 HPAI virus, but did increase survival associated with H5N1 HPAI virus infection. The magnitude of this effect on the outcome of the H5N1 HPAI virus infection varied between different LPAI viruses, and was associated both with efficiency of LPAI viral replication in wood ducks and the development of a detectable humoral immune response. These observations suggest that in naturally occurring outbreaks of H5N1 HPAI, birds with pre-existing immunity to homologous hemagglutinin or neuraminidase subtypes of AI virus may either survive H5N1 HPAI virus infection or live longer than naïve birds and, consequently, could pose a greater risk for contributing to viral transmission and dissemination. The mechanisms responsible for this protection and/or the duration of this immunity remain unknown. The results of this study are important for surveillance efforts and help clarify epidemiological data from outbreaks of H5N1 HPAI virus in wild bird populations.

Effect of a prior exposure to a low pathogenic avian influenza virus in the outcome of a heterosubtypic low pathogenic avian influenza infection in mallards (Anas platyrhynchos).

Wild birds, particularly Anseriformes and Charadriiformes, are considered the natural reservoir of low pathogenic avian influenza (LPAI) viruses. The high prevalence and subtype diversity of avian influenza viruses at premigrational staging areas provide the perfect opportunity for multiple exposures to different LPAI virus subtypes. Natural consecutive and concurrent infections of sentinel ducks with different LPAI virus subtypes have been reported. The protective immune response from different LPAI virus infections is not understood nor is the effect of such repeated exposures. This study experimentally evaluated the effect of a prior exposure to a LPAI virus on the outcome of a heterosubtypic LPAI virus infection in mallards (Anas platyrhynchos). The results of this investigation suggest that recent prior exposure to a LPAI virus may affect the outcome of a subsequent heterosubtypic LPAI infection in mallards by reducing the duration of cloacal and oropharyngeal viral shedding as well as the viral load excreted via the cloaca. Wild mallards are likely exposed to multiple subtypes of LPAI virus during the periods of peak viral circulation, and the results of this study suggest that the duration of viral shedding in subsequent exposures might be reduced.

[Comparison between coproparasitological techniques for the diagnosis of helminth eggs or protozoa oocysts in dogs]. / Comparação entre técnicas coproparasitológicas no diagnóstico de ovos de helmintos e oocistos de protozoários em cães.

In this study we evaluated the frequency of enteroparasites in pet dogs and their association with age, sex and breed, as well as the efficiency of the Willis-Mollay, Faust, Sedimentation and Direct exam methods. By these methods we processed 401 fecal samples. The samples were positive in the following percentages: Ancylostoma spp. (53.1%), Toxocara canis (20.7%), Cystoisospora ohioensis (15.7%), Trichuris vulpis (3.7%), Dipylidium caninum (2.5%) and Taenia spp. (1.0%). Toxocara canis (67.3%) and C. ohioensis (47.3%) showed higher positivity in the puppies. The Willis-Mollay technique was more efficient in the diagnosis of Ancylostoma spp. and T. canis eggs. The Direct method was the least efficient. It was found that the majority of the cases of D. caninum were diagnosed by the Sedimentation method (8=2.0%), while for T. vulpis Willis-Mollay (12=3.0%) and Sedimentation (13=3.2%) were more efficient. In view of these results, we can recommend the association of Willis-Mollay and Sedimentation methods for the diagnosis of gastrointestinal helminths. Due to the elevated occurrence of Ancylostoma spp. and T. canis, which are involved in zoonotic diseases, it becomes necessary to apply more efficient prophylaxis of canine intestinal parasitosis at the City of Araçatuba, state of São Paulo.