Detection of avian influenza viruses from shorebirds: evaluation of surveillance and testing approaches

Although influenza A viruses have been isolated from numerous shorebird species (Family: Scolopacidae) worldwide, our understanding of natural history of these viruses in this diverse group is incomplete. Gaining this information can be complicated by sampling difficulties related to live capture, the need for large sample sizes related to a potentially low prevalence of infection, and the need to maintain flexibility in diagnostic approaches related to varied capabilities and resources. To provide information relevant to improving sampling and testing of shorebirds for influenza A viruses, we retrospectively evaluated a combined data set from Delaware Bay, USA, collected from 2000 to 2009. Our results indicate that prevalence trends and subtype diversity can be effectively determined by either direct sampling of birds or indirect sampling of feces; however, the extent of detected subtype diversity is a function of the number of viruses recovered during that year. Even in cases where a large number of viruses are identified, an underestimate of true subtype diversity is likely. Influenza A virus isolation from Ruddy Turnstones can be enhanced by testing both cloacal and tracheal samples, and matrix real-time PCR can be used as an effective screening tool. Serologic testing to target species of interest also has application to shorebird surveillance. Overall, all of the sampling and diagnostic approaches have utility as applied to shorebird surveillance, but all are associated with inherent biases that need to be considered when comparing results from independent studies.

Animal health surveillance: navigation amidst the flotsam of human frailty and fiscal inertia

National veterinary services monitor endemic, emerging and exotic disease situations. They intervene when epidemic tendencies demand. They unravel complex disease situations. They do so as monopolies, in environments of political influence and budgetary restraint. When human, animal health and trade protection dictate, they design import or domestic disease control programs. As much as 80% of program expenditures are on surveillance. Their initiatives are scrutinized by treasuries from which they seek funding, industries from which they seek collaboration and trading partners from whom they seek recognition. In democracies, surveillance and control programs are often the products of a complicated consultative process. It involves individuals who have both a commitment to improving an existing animal health situation and access to the required resources. The generations that designed traditionally risk-averse national surveillance and control programs have given way to a new one which is more epidemiologically informed. Their successors design programs bearing epidemiologically based improvements. The transition, however, has not been overwhelmingly welcomed. Expenditures on surveillance are tolerated out of fear during outbreaks of foreign or re-emergence of indigenous disease. Between epidemics, they decline at the hands of producers' unwillingness and budgetary restraint. Human nature responds to the high cost of surveillance in forms ranging from naïveté through to conspiracy. While legislation cannot subdue such human frailty, several other opportunities exist. Education can remove the majority of problems caused by ignorance, leaving the minority that arise intentionally. Technology decreases the high cost of testing which tempts individuals to cut corners. International standards assist National Veterinary Services to overcome domestic resistance.

[Surveillance and forecast of Schistosoma japonicum-infected sentinel mice in key water regions of China in 2010]

OBJECTIVE

To explore the approach and tool for surveillance and forecast of schistosomiasis, so as to provide scientific evidence for improving the sensitivity of the surveillance and forecast system of schistosomiasis.

METHODS

Two field detections were carried out in June and September by using the determination of sentinel mice in key high-risk water regions of 7 provinces of Hunan, Hubei, Jiangxi, Anhui, Jiangsu, Yunnan and Sichuan, and the sentinel mice were raised in laboratory and dissected for observation of schistosome infections. The database regarding schisosome infections in key water regions of China was established, and the tempo-spatial distribution and environmental features of the national surveillance and forecast sites with positive sentinel mice were analyzed.

RESULTS

A total of 72 surveillance and forecast sites were detected in 34 counties (cities, districts) of 7 provinces. Of the 2 667 sentinel mice placed, 2 613 were recovered, with a recovery rate of 97.98%. Among the 72 sites detected, 17 were detected with positive sentinel mice, and the occurrence rate of positive sites was 23.61%. The occurrence rate was 17.24% (10/58) in June and 14.71% (10/68) in September, and no significant difference was observed between two batches (chi2 = 0.151, P = 0.698). Of the 2 436 sentinel mice dissected, 90 were positive, and 459 schistosome worms were collected, with a total infection rate of 3.69%, and the mean worm burdens of positive mice were 5.10 worms per mouse. The infection rate of sentinel mice was 2.82% (31/1 099) in June and 4.41% (58/1 337) in September, the infection rate of sentinel mice was significantly higher in September than that in Juen (chi2 = 14.681, P < 0.01), and the mean worm burdens of infected sentinel mice were 2.45 worms per mouse in June and 6.49 worms per mouse in September. The occurrence rates of the positive sites with infected snails detected in the study year, last year and without infected snails detected in recent 3 years were 29.63%, 41.67% and 12.12%, respectively, and no significant differences were detected (chi2 = 5.227, P = 0.071). The infection rates of sentinel mice in the aforementioned 3 settings were 9.38%, 3.98% and 0.59%, respectively, and there was significant difference observed (chi2 = 20.489, P < 0.01).

CONCLUSIONS

The monitoring results of sentinel mice infections in key water regions can almost reflect the endemic situation of schistosomiasis in local areas. Notably, many infections are detected in settings without infected snails detected in recent years. The monitoring of sentinel mice infections could significantly improve the sensitivity of the surveillance and forecast system of schistosomiasis.

Use of observed wild bird activity on poultry farms and a literature review to target species as high priority for avian influenza testing in 2 regions of Canada

The risk of avian influenza outbreaks in poultry is partially dependent on the probability of contact between domestic poultry and wild birds shedding avian influenza (AI) virus. The major objective of this study was to document wild bird activity on poultry farms to determine which wild bird species should be targeted for AI surveillance in Canada. We collected data in 2 major poultry producing regions of Canada, southwestern Ontario and the Fraser Valley of British Columbia, on the relative abundance of various wild bird species found on poultry farms and on how these species utilized habitat around poultry farms. We reviewed the published literature to determine what was known about AI pathobiology in the species we observed. From these results we created a list of 10 wild bird species that are a priority for further study. These species are the European starling, barn swallow, rock dove, American crow, northwestern crow, American robin, dark-eyed junco, song sparrow, horned lark, and common grackle. Abundance of these and other species varied between provinces and seasons.

Serological and clinical surveillance studies to validate reported foot-and-mouth disease free status in Tsirang district of Bhutan

Serological and clinical studies were conducted between March 2009 and August 2010 to validate the foot-and-mouth disease free status of Tsirang district of Bhutan as determined by the country's passive surveillance system. Randomised (first survey) and targeted (third survey) samplings, with subsequent follow-up samplings (second and fourth), were conducted on FMD-susceptible animals to detect the disease at a design prevalence of 25% and 20% at the individual animal-level and village-level, respectively. Sera from cattle, goats, pigs, and sheep were tested for the presence of non-structural protein (NSP) antibodies using two commercial (PrioCHECK(®) FMDV NS and CHEKIT(®)-FMD-3ABC-bo-ov) and one in-house NSP kit (c-ELISA, AAHL, Australia). The overall seropositivity (all species) at the animal-level was 3% (95% CI: 1.7, 4.8) and 3.5% (95% CI: 2.1, 5.4), for the randomised and targeted surveys, respectively. Except for one goat from the first survey, none of the small ruminants and pigs had NSP antibodies. The seropositives from the first and targeted surveys were distributed among 13 and 16 of 20 villages sampled, respectively. All repeat testing from the initial seropositive animals and their herd mates, for both the first and third surveys, were negative in the NSP tests 6-8 months later. Using the hypergeometric exact probability formula for two-stage analyses, the results enabled rejection of the null hypothesis and supported conclusion that the population was free from disease at the minimum expected prevalence of 20% at the 95.53% and 99.46% confidence levels, for the randomised and targeted surveys, respectively. Clinical surveillance also showed absence of disease or clinical signs suggestive of FMD. The few seropositives were likely to be false positives due to factors such as imperfect specificities of the tests and possible NSP-residues in the vaccines. The study has paved the way for initiation of zoning approaches for the progressive control of FMD in Bhutan.

Rapid screening for sentinel chicken seroconversions against arboviruses

A novel test procedure can screen seroconversions in sentinel chickens with the commercially available VecTest designed to detect viral antigens, such as West Nile virus. The test requires minimum laboratory equipment and skills, and provides qualitative results in about 45 min, which are immediately available to vector control agencies for making decisions to manage mosquito populations in order to interrupt arbovirus transmission.

Priority areas for surveillance and prevention of avian influenza during the water-bird migration season in Pakistan

Avian influenza viruses may be introduced into domestic poultry through migratory wild birds, particularly from Pakistan, which is situated across the migratory Indus flyway and holds more than 225 wetlands. To answer the question which areas should be given priority in surveillance and prevention with respect to notifiable avian influenza during the migratory season, a subset of Asian waterbird census data was reviewed. The dataset contains 535 local sites and available counts of waterbirds reported from 1987 to 2007. However, as the majority of the sites are not counted regularly gaps in data matrix appeared. The coordinates of 270 known sites completely fitted the administrative boundaries of the country. These coordinates were geo-processed with polygons of water-bodies and a raster map of predicted poultry density. Pixels representing the estimated number of poultry per km2 were found within a 3 to 9 km range of the census sites (or water-bodies) in their proximity. The coordinates were also used to map the maximum reported counts of waterbirds and local clusters of under-sampled sites. A retrospective case-series analysis of previous outbreaks (2006-2008) of influenza A virus, subtype H5N1 was performed, which revealed that 64% of outbreaks, reported to Office International des Epizooties, the World Organization for Animal Health, occurred during the migratory period. This paper highlights the potential use and limitations of the Asian waterbirds census data in the context of avian influenza. The proposed methodology may be used to prioritize districts for surveillance and economize prevention measures provided better data are generated in future.

Canine distemper spillover in domestic dogs from urban wildlife

Canine distemper virus (CDV) causes a major disease of domestic dogs that develops as a serious systemic infection in unvaccinated or improperly vaccinated dogs. Domesticated dogs are the main reservoir of CDV, a multihost pathogen. This virus of the genus Morbillivirus in the family Paramyxoviridae occurs in other carnivorous species including all members of the Canidae and Mustelidae families and in some members of the Procyonidae, Hyaenidae, Ursidae, and Viverridae families. Canine distemper also has been reported in the Felidae family and marine mammals. The spread and incidences of CDV epidemics in dogs and wildlife here and worldwide are increasing.

Spatial patterns of recorded mastitis incidence and somatic cell counts in Swedish dairy cows: implications for surveillance

Clinical mastitis (CM) is the most common veterinary treated disease in Swedish dairy cattle. To investigate if the distribution of veterinary registered cases of CM in Sweden follows that of the spatial distribution of cows with high somatic cell counts (SCCs), the spatial distribution of CM odds was estimated from available records and compared with udder health measures based on measurements of SCC derived from official milk recording. The study revealed areas with significantly lower odds for CM but with a high proportion of cows with a poor udder health score, suggesting an under-reporting of CM. We also found areas of significantly higher odds for CM despite a low proportion of cows with a poor udder health score, suggestive of over-treatment of mastitis. The results should enable targeted studies of reasons for discrepancies, e.g. farmers' and veterinarians' attitudes to mastitis treatment and disease recording in areas with a deficit or excess of registered CM cases. High quality disease records for dairy cattle are of interest not only for the dairy management but also for disease surveillance, monitoring of use of antibiotics and food safety purposes.