Direct and indirect contact rates among livestock operations in Colorado and Kansas.

OBJECTIVE: To characterize direct and indirect contacts among livestock operations in Colorado and Kansas. DESIGN: Cross-sectional quarterly survey. SAMPLE: 532 livestock producers. PROCEDURES: Livestock producers in Colorado and Kansas were recruited by various means to participate in the survey, which was sent out via email or postal mail once quarterly (in March, June, September, and December) throughout 2011. Data were entered into an electronic record, and descriptive statistics were summarized. RESULTS: Large swine operations moving animals to other large swine operations had the highest outgoing direct contact rates (range, 5.9 to 24.53/quarter), followed by dairy operations moving cattle to auction or other dairy operations (range, 2.6 to 10.34/quarter). Incoming direct contact rates for most quarters were highest for large feedlots (range, 0 to 11.56/quarter) and dairies (range, 3.90 to 5.78/quarter). For large feedlots, mean total indirect contacts through feed trucks, livestock haulers, and manure haulers each exceeded 725 for the year. Dairy operations had a mean of 434.25 indirect contacts from milk trucks and 282.25 from manure haulers for the year. CONCLUSIONS AND CLINICAL RELEVANCE: High direct contact rates detected among large swine operations may suggest a risk for direct disease transmission within the integrated swine system. Indirect contacts as well as incoming direct contacts may put large feedlots at substantial risk for disease introduction. These data can be useful for establishing and evaluating policy and biosecurity guidelines for livestock producers in the central United States. The results may be used to inform efforts to model transmission and control of infectious diseases such as foot-and-mouth disease in this region.

Phylogenetic analysis of influenza A viruses (H6N8, H1N8, H4N2, H9N2, H10N7) isolated from wild birds, ducks, and ostriches in South Africa from 2007 to 2009.

Influenza A strains emerging from wild birds are a constant threat to South Africa's valuable ostrich industry. In 2004 and again in 2006, low pathogenicity avian influenza H5N2 strains introduced from a wild bird reservoir mutated in ostriches to high pathogenicity avian influenza (HPAI), with serious economic consequences and export bans imposed by the European Union. Although no outbreaks of notifiable avian influenza have occurred in South Africa since 2006, the H9N2 virus caused a localized outbreak where ostriches displayed symptoms of green urine, depression, and mild morbidity. Most recently, an outbreak of H10N7 in farmed Pekin ducks (Anas platyrhynchos domestica) caused increased mortalities, but this was exacerbated by a secondary Escherichia coli infection, because an intravenous pathogenicity index of 0.00 was recorded. Each of the eight gene segments of the five strains isolated from 2007 to 2009 from farmed ostriches in the Oudtshoorn region (H6N8, H9N2), Pekin ducks (H10N7, Joostenburgvlakte region), and wild Egyptian geese (Alopochen aegypticus; H1N8, Baberspan wetlands; H4N2, Oudtshoorn region) were sequenced, genetically analyzed, and compared to previous South African isolates and viruses in the public data banks. An H5N8 strain was also detected by reverse-transcription PCR in cloacal swabs from swift terns (Sterna bergii) in the Mosselbaai region during 2007, although a virus could not be isolated. Initial phylogenetic results indicate that H6N8 and H9N2 ostrich and H10N7 Pekin duck viruses originated in the wild bird population that is geographically dispersed throughout southern Africa, based on the reassortment of viral genes from birds sampled outside of the ostrich farming areas. No evidence of internal genes associated with Asian HPAI H5N1 strains were detected in the South African isolates.

Risk factors for seropositivity to H5 avian influenza virus in ostrich farms in the Western Cape Province, South Africa.

In a 2005 serological survey, carried out in response to an outbreak of H5N2 avian influenza (AI) in ostriches in the Eastern Cape Province, 16.3% of ostrich farms in the Western Cape Province of South Africa were found to be seropositive to H5 AI virus. We subsequently carried out a questionnaire-based census survey on all available registered Western Cape ostrich farms that still existed at the end of 2005 (367 farms, of which 82 were seropositive), in order to identify risk factors associated with farm-level seropositivity. A farm was classified as seropositive for H5 AI virus if one or more birds had tested positive (haemagglutination inhibition titre >1:16) in the 2005 survey, which had been designed to detect a minimum within-group seroprevalence of 10%. For each farm, risk factor information was collected using a questionnaire administered during a face-to-face interview with each farm owner or manager. Information was obtained on the ostrich population, movements of birds, environmental factors, management practices, and frequency of contact between ostriches and various wild bird species. Multiple logistic regression models were developed for the whole Western Cape Province and also for the two largest ostrich farming regions, "Klein Karoo" and "Southern Cape". Seroprevalence differed between regions, being highest in the Klein Karoo (31.6%). In all three models, increased risk of farm-level H5 AI virus seropositivity was associated with increasing numbers of ostriches, excluding chicks, present on the farm. Increased risk of seropositivity was associated with reduced frequency of cleaning of feed troughs (<1x/week vs. >1x/week), both overall (odds ratio (OR)=4.5; 95% confidence interval (CI): 1.5, 13.3) and in the Southern Cape (OR=53.6; 95% CI: 3.3, 864), and with failure to clean and disinfect transport vehicles, both overall (OR=2.3; 95% CI: 1.1, 4.8) and in the Klein Karoo (OR=2.6; 95% CI: 1.1, 6.5). Increased risk of seropositivity was also associated with increasing frequency of contact of ostriches with certain wild bird species: overall with white storks (Ciconia ciconia), in the Southern Cape with gulls (Larus spp.), and in the Klein Karoo with Egyptian geese (Alopochen aegyptiaca).