Longevity of Ceratomyxa shasta and Parvicapsula minibicornis actinospore infectivity in the Klamath River

Infectious Ceratomyxa shasta and Parvicapsula minibicornis actinospores were present in Klamath River samples collected in April, May, and June 2005. Juvenile Chinook salmon Oncorhynchus tshawytscha exposed to river water maintained at the ambient Klamath River temperature for 0, 4, 24, 72, and 168 h (7 d) developed asymptomatic infections from both parasites. Elevated water temperature (18 degrees C) in June may have reduced actinospore viability, as both C. shasta and P. minibicornis infection markedly declined in fish exposed for over 72 h. As judged by the prevalence of infection for both parasites, the number of infectious actinospores tended to increase or remain steady through the spring. Ceratomyxa shasta infections were characterized by the presence of a few trophozoites within granulomatous foci in mesentery adipose tissue and were consistently observed outside of the intestine. Similarly, low numbers of P. minibicornis were observed in kidney glomeruli and tubules but were not associated with inflammation. Parvicapsula minibicornis DNA was consistently detected by quantitative real-time polymerase chain reaction in filtered water samples collected each month and from each time posttransfer. These data and the high prevalence of infection observed in the exposed fish indicate that P. minibicornis actinospores were at a relatively high concentration in the river during the spring. In contrast, C. shasta DNA was only detected in half of the water sample sets and its detection did not correspond well to C. shasta infectivity. An approximately threefold increase in river flow from the April to the May water collection was not associated with a decline in either the detection of actinospores (particularly for P. minibicornis) or the prevalence of infection for both parasites. Actinospores of these myxosporean parasites have the potential to infect salmonids for at least 7 d after release from the alternate polychaete host.     

Survey of pathogens in hatchery Chinook salmon with different out-migration histories through the Snake and Columbia rivers

The operation of the Federal Columbia River Power System (FCRPS) has negatively affected threatened and endangered salmonid populations in the Pacific Northwest. Barging Snake River spring Chinook salmon Oncorhynchus tshawytscha through the FCRPS is one effort to mitigate the effect of the hydrosystem on juvenile salmon out-migration. However, little is known about the occurrence and transmission of infectious agents in barged juvenile salmon relative to juvenile salmon that remain in-river to navigate to the ocean. We conducted a survey of hatchery-reared spring Chinook salmon at various points along their out-migration path as they left their natal hatcheries and either migrated in-river or were barged through the FCRPS. Salmon kidneys were screened by polymerase chain reaction for nine pathogens and one family of water molds. Eight pathogens were detected; the most prevalent were Renibacterium salmoninarum and infectious hematopoietic necrosis virus. Species in the family Saprolegniaceae were also commonly detected. Pathogen prevalence was significantly greater in fish that were barged through the FCRPS than in fish left to out-migrate in-river. These results suggest that the transmission of infectious agents to susceptible juvenile salmon occurs during the barging process. Therefore, management activities that reduce pathogen exposure during barging may increase the survival of juvenile Chinook salmon after they are released.     

The effects of changing demographics on the distribution of marine anemia in farmed salmon in British Columbia.

The changing geographic distribution of marine anemia (plasmacytoid leukemia) was compared with the evolving demographics of the chinook farming industry in British Columbia to explore the hypothesis that the disease had spread throughout the province between 1987 and 1992. Through retrospective and prospective methods, it was shown that the apparent spread of the disease was likely an artifact, resulting from changes in the distribution of fish farms throughout the province and corresponding changes in the intensity of regional disease surveillance. When viewed over a 5-year period, there were no statistically significant differences in the prevalence of the disease amongst fish sampled from each of the major salmon farming regions of British Columbia. By increasing the intensity of surveillance for the disease in apparently negative regions or chinook farms, one could routinely find cases of the disease. The results suggest that marine anemia is an endemic problem for farmed chinook salmon in British Columbia and is not a spreading epidemic.     

Fusariotoxicosis from barley in British Columbia. I. Natural occurrence and diagnosis.

Clinical sickness was observed in domestic ducks, geese, horses and swine during October 1973. All species showed upper alimentary distress with mortalities occurring in the geese. Barley derived from a common source had been fed. Examination of the barley revealed invasion by Fusarium spp and detection of a high level of dermatitic fusariotoxins.     

Fusariotoxicosis from barley in British Columbia. II. Analysis and toxicity of syspected barley.

Fusariotoxin T-2, a trichothecene, was tentatively identified in barley samples which caused field outbreaks of mycotoxicosis in British Columbia. Geese died when fed the contaminated barley experimentally but mice were little affected after long term feeding. The methods used in the laboratory for trichothecene extraction and identification of T-2 toxin are described.     

Associations of antimicrobial uses with antimicrobial resistance of fecal Escherichia coli from pigs on 47 farrow-to-finish farms in Ontario and British Columbia

This study assessed the associations between antimicrobial use and other management practices in pigs and antimicrobial resistance in generic Escherichia coli recovered from feces of weaner and finisher pigs on 39 purposefully selected farrow-to-finish farms in Ontario and 8 in British Columbia. Antimicrobials (n = 13), most frequently penicillins and tetracycline, wer dministered to different age groups of pigs on study farms through various routes of administration. Logistic regression was used to model risk factors to antimicrobial resistance in fecal E. coli of pigs for the following antimicrobials: ampicillin, apramycin, carbadox, cephalothin, chloramphenicol, kanamycin, neomycin, nitrofurantoin, spectinomycin, streptomycin, sulfamethoxazole tetracycline, and cotrimoxazole (trimethoprim and sulfamethoxazole). Use of antimicrobials in weaner pigs compared with use in finisher pigs was associated with resistance in most models. There was phenotypic evidence of different mechanisms of resistance selection, including direct selection [use of carbadox was associated with carbadox resistance (OR = 6.48)]; cross-resistance [use of spectinomycin was associated with streptomycin resistance (OR = 2.29)]; and possible co-selection [ceftiofu use was associated with tetracycline resistance (OR = 6.12)]. These results provide further evidence that use of antimicrobials in pigs selects for resistance among fecal E. coli within and between classes of antimicrobials.     

Comparison of macrophage scavenger receptor-A knockout mice with wild type ones in the immune response against repeated infestation with Haemaphysalis longicornis

Using macrophage scavenger receptor-A knockout (SRKO) mice, we examined the role of macrophage class A scavenger receptors (MRS-A) on the immune response and acquisition of host resistance against repeated infestation with Haemaphysalis longicornis. Except for one batch of nymphs that infested one of the SRKO (SR-/-) mice and showed no appreciable reduction in body weight, all the other groups of nymphs manifested significant decrease in body weight. Both SR-/- and wild type (SR+/+) mice showed a sustained increase in anti-tick antibody titers, but SR+/+ mice showed significantly higher titers. The IFN-gamma assayed in SR-/- mouse immune sera was substantially less compared with that in SR+/+ mice. Immune sera from SR-/- and SR+/+ mice recognized the 51 and 44 kDa, and 44 kDa proteins, respectively, of the salivary gland antigen. The difference in the level of anti-tick resistance manifested by both groups of mice may be influenced by less efficient trapping and processing of tick antigens by macrophages in mice lacking for the macrophage scavenger receptors, and consequently affected the cascade of Th1 and Th2 responses. We have thus obtained valuable data that strongly infer the role of MSR-A in enhancing host defense against repeated infestation with H. longicornis.     

Virus characterization, clinical presentation, and pathology associated with H7N3 avian influenza in British Columbia broiler breeder chickens in 2004

Low-pathogenicity avian influenza (LPAI) subtype H7N3 was diagnosed on a two-age broiler breeder farm in Abbotsford, British Columbia (BC), in early February 2004. The presenting complaint in the older index flock was feed refusal, with 0.5% mortality over 72 hr that resolved over the following week Ten days after the initial complaint in the index flock, a younger flock in an adjacent barn experienced an abrupt spike in mortality (25% in 48 hr). The gross lesions of tracheal hyperemia and hilar pulmonary consolidation were subtle and nonspecific, and the diagnosis of avian influenza required laboratory confirmation. Two different viruses were isolated from the index farm: a LPAI (H7N3) was isolated from the older flock and a high-pathogenicity avian influenza (HPAI) (H7N3), which had an additional 21 base insertion at the hemagglutinin-cleavage site, was isolated from the younger flock. The presence of this insertion sequence and the similarity of adjacent sequences indicate that the LPAI had mutated into HPAI at some point between the first and second barn. Despite enhanced on-farm biosecurity measures, the virus was not contained on the index farm and eventually spread to over 40 commercial poultry facilities before massive depopulation efforts enabled its eradication.     

Investigation of the Concurrent Emergence of Salmonella enteritidis in Humans and Poultry in British Columbia,Canada, 2008–2010

An increase in the rate of human infections with Salmonella enteritidis (SE) occurred between 2007 and 2010 in British Columbia (BC). During the same time period, an increase in SE from poultry‐sourced isolates and increased clinical severity in poultry were also observed in BC. This article describes a multi‐sectoral collaboration during a 3‐year investigation, and the actions taken by public health and animal health professionals. Human cases were interviewed, clusters were investigated, and a case–control study was conducted. Environmental investigations were conducted in food service establishments (FSE). Suspect foods were tested. Laboratory data from poultry‐sourced isolates were analysed. Five hundred and eighty‐four human cases of SE with the same pulsed‐field gel electrophoresis pattern were identified between May 2008 and August 2010. Seventy‐three percentage of cases reported consumption of eggs. The odds of egg consumption were 2.4 times higher for cases than controls. Implicated FSE were found to use ungraded eggs, which had been distributed illegally. Investigation suggested that there were multiple suppliers of these eggs. Collaboration between public health and animal health professionals led to data sharing, improved understanding of SE, engagement with the poultry industry and public communication. Multi‐disciplinary, multi‐sectoral and multi‐pronged investigations are recommended to identify the likely source of illness in large, protracted foodborne outbreaks caused by commonly consumed foods.     

Prevalence and patterns of antimicrobial resistance of fecal Escherichia coli among pigs on 47 farrow-to-finish farms with different in-feed medication policies in Ontario and British Columbia

The main objectives of this study were to determine the prevalence and patterns of antimicrobial resistance in pigs on farms that medicated swine ration and those that did not. A total of 940 isolates of Escherichia coli from 188 pooled fecal samples obtained from weaner and finisher pigs on 47 farrow-to-finish swine farms (34 farms used in-feed medication and 13 did not) were tested for susceptibility to 21 antimicrobials using a breakpoint concentration method. The prevalence of resistance varied widely (0.0% to 81.3%) among the antimicrobials tested. Ninety percent of all the isolates tested were resistant to one or more antimicrobials. The most common multi-drug resistance patterns were to 2 to 6 antimicrobials. Resistance was significantly more frequent (P < 0.01) on farms that used in-feed medication compared to those that did not, and significantly more frequent (P < 0.01) in weaner pigs compared to finisher pigs. These findings indicate that resistance to a broad range of antimicrobials was prevalent among fecal E. coli isolates of pigs on study farms, and that this constitutes a potential reservoir for resistance genes that could spread to pathogens. The findings also provide further evidence that use of medication in swine rations provides selective pressure for antimicrobial resistance in E. coli in pigs.     

Echinococcus multilocularis in red foxes in Saxony-Anhalt: identification of areas of increased risk of infestation and association of the infestation probability with the average annual maximum temperature

Between 1998 and 2004 1341 Red Foxes from 611 locations were examined parasitologically for Echinococcus multilocularis at the State Office of Consumer Protection Saxony-Anhalt. Examination was carried out in parallel to rabies monitoring. A period-prevalence of 9.2% of infestation was found. Employing a Scan Statistic a large area in the southwest of the federal state and two smaller areas of increased risk with respect to infestation with Echinococcus multilocularis were identified. The hypothesis of a negative association of the probability of infestation with the average annual maximum temperature of the location where the foxes were shot was supported by logistic regression analysis. A decreased probability of inactivation of Echinococcus multilocularis-oncospheres through heat and desiccation in areas of lower average annual maximum temperature seems to be likely.Thus, the infection pressure increases with reduced temperatures.     

A field study on the usefulness of milk progesterone determination to confirm estrus and pregnancy of dairy cows in the Fraser Valley area of British Columbia

A field study was conducted to determine the usefulness of milk progesterone determination at the time of breeding to confirm estrus and at 21 days postbreeding to detect open cows. Twenty-seven dairy farmers collaborated in this study by providing milk samples on the day of breeding and 21 days later, together with pregnancy diagnosis data and information on herd reproductive management. Herd size ranged from 15 to 175 cows, the average being 65 milking cows. Six hundred and sixty-seven breeding-day samples and 472, 21-day samples were provided by the farmers. Analysis of milk samples for progesterone by a solid phase radioimmunoassay showed that only 32 (4.8%) of the services were performed when the cow was not in estrus (progesterone > 1 ng/mL). Of the 472, 21-day samples, 337 (71%) showed progesterone levels of > 1 ng/mL, while 135 (29%) showed progesterone levels of < 1 ng/mL. Subsequently, 243 (72%) of the cows with progesterone > 1 ng/mL and eight (6%) of the cows with progesterone < 1 ng/mL were diagnosed pregnant by transrectal palpation, giving a pregnancy rate of 53%. Progesterone concentration on the day of breeding was not associated with season or herd size. However, progesterone concentration at 21 days and pregnancy rate were associated with herd size. These results indicate that fertillzation failure and/or early embryonic mortality, rather than inaccurate detection of estrus, are the major reproductive problems encountered by the dairy farmers in British Columbia. Furthermore, progesterone values at 21 days were closely related to reproductive status and indicate the usefulness of milk progesterone assay for the early detection of open cows.