Relationship Between Weather and Changes in Annual and Seasonal Abundance of Culicoides sonorensis (Diptera: Ceratopogonidae) in Alberta.

Factors influencing annual and seasonal abundance of Culicoides sonorensis (Wirth and Jones) (Diptera; Ceratopogonidae) were examined at 10 sites in southern Alberta using negative binomial regression. Annual abundance varied among locations with greatest abundance in a narrow geographic band between -112.17 and -112.64°W longitude and 49.32 and 50.17°N latitude. Sites were grouped depending on whether abundance was continuous and high; discontinuous and low; or sporadic and low without much loss of information. Maximum annual abundance declined with spring precipitation, increased with spring temperature, and was unrelated to spring relative humidity, suggesting that abundance is highest during years with early drought conditions. Seasonal abundance was associated with the same factors but was further influenced by temperature and relative humidity during the sample intervals. Lagged effects were apparent, suggesting abundance increased with warmer temperatures over a six-week period, and increased when relative humidity declined closer to the sampling period. Predicted values were slightly biased and tended to overestimate observed data, but this could be adjusted using calibration curves. The model can also be used to predict presence/absence of C. sonorensis and will be useful for developing risk assessments.

Altered GABAA α5 subunit expression in the hypothalamic paraventricular nucleus of hypertensive and pregnant rats.

A characteristic of both hypertension and pregnancy is increased sympathetic nerve activity. The level of sympathetic activation is determined, in part, by a tonic GABAergic inhibition arising from the hypothalamic paraventricular nucleus (PVN). In hypertension, decreases in GABAergic inhibition and increases in glutamatergic excitation within the PVN contribute to this sympatho-excitation. In late-term pregnancy however, the sympatho-excitation appears to be mediated by decreases in GABAergic inhibition only. This study examined whether changes in subunit expression for GABAA receptors in the PVN could provide a molecular basis for the sympatho-excitation characteristic of hypertension and pregnancy. Hypertension and pregnancy were accompanied by significant decrease in the GABAA receptor α5 subunit in the PVN. We suggest that decreases in the α5 subunit of the GABAA receptor may be important in mediating the sympatho-excitation observed in both hypertension and pregnancy.

Simulation modelling of a hypothetical introduction of foot-and-mouth disease into Alberta.

This study describes the use of simulation modelling to evaluate the predicted benefits of an effective livestock traceability system in responding to a hypothetical introduction of foot-and-mouth disease (FMD) in to the province of Alberta, Canada, and whether or not the implementation of emergency ring vaccination in addition to a standard stamping-out (SO) strategy would lead to smaller and shorter epidemics. Three introduction scenarios were defined, with the primary case in either an intensive beef feedlot operation, an extensive cow-calf operation or in a swine operation. Disease spread was simulated using, three levels of tracing effectiveness, five types of vaccination zone, three different vaccination start times, three lengths of vaccination campaigns, two levels of culling resource and using FMD strains with two different virulence levels. Using standard SO procedures (without vaccination), improving traceability effectiveness from a level whereby only 65% of movements were traced within 5-7 days, to a capability whereby all movements were traced within 1 day, led to a reduction in the number of infected premises (IPs) between 18.7 and 64.5%, an average saving of CAN$29,000,000 in livestock compensation costs alone, and a reduction in the length of epidemics ranging from 1 to 22 days. The implementation of emergency vaccination also led to a reduction in the number of IPs and a shortening of epidemics. The effects were more pronounced when the higher virulence settings were used, with a predicted reduction in IPs of 16.6-68.7% (mean=48.6%) and epidemics shortened by up to 37 days. Multi-variable analyses showed these effects were highly significant, after accounting for the incursion location, virulence of virus and time of first detection. The results clearly demonstrated the benefits of having effective traceability systems with rapid query and reporting functionality. The results also supported the value of early vaccination as an adjunct to SO in reducing the number of IPs and shortening the length of the epidemics. The most effective vaccination strategy involved a 3 km or larger suppressive vaccination zone around all IPs, begun as soon as practicable after first detection, and which continued until the last IP was detected.

Surveillance for avian influenza virus subtypes H5 and H7 in chickens and turkeys farmed commercially in New Zealand.

AIM: To determine the status of avian influenza (AI) virus sub-types H5 and H7 of New Zealand's commercial chicken and turkey farms. METHODS: A cross-sectional serological survey, stratified by production sector, used a sample frame defined by those farms registered with the Poultry Industry Association of New Zealand (PIANZ) or the Egg Producers Federation of New Zealand (EPF). Sectors included were chicken broiler, caged/barn layer, free-range layer, pullet rearer and turkey broiler. The survey used a between- and within-farm design prevalence of 5% (95% confidence for chickens, 99% confidence for turkeys) and 30% (95% confidence), respectively, of AI virus subtypes H5 and H7. The epidemiological unit was the farm for the free-range layer sector, and the individual shed/barn for the other sectors. Serum samples were screened using a commercial generic influenza A indirect ELISA; positive samples were subjected to haemagglutination-inhibition (HI) testing for AI virus subtypes H5 and H7. A comprehensive investigation, that included widespread serological and antigenic screening, was carried out on all farms identified with serum reactors to either the H5 or H7 virus subtype. RESULTS: A total of 4,180 blood samples from 167 chicken and 10 turkey farms were collected and tested using ELISA. Positive ELISA results were returned from 26 farms, comprising 10 caged/barn layer, 14 free-range layer and two turkey (shed-raised) broiler farms. HI testing of ELISA-positive sera for the H7 subtype virus identified no positive sera in any sector. Reactors to the H5 subtype virus were limited to three free-range layer chicken farms; each farm returned a single serum reactor. Follow-up investigations on these free-range farms identified evidence of historic exposure to the H5 subtype virus on one farm, and concluded that the serum reactors identified in the initial sampling round on the other two farms were non-specific (false-positive) reactions. CONCLUSIONS: The survey found no evidence of active infection with notifiable AI viruses, and provided evidence of absence of exposure to AI virus subtypes H5 and H7 in the chicken broiler, caged/barn layer, turkey broiler and pullet-rearer sectors at a between- and within-farm prevalence of 5% and 30%, respectively, with 95% confidence. The results established commercial free-range layer farms as a risk sector for exposure to notifiable AI virus.

A cross-sectional survey of influenza A infection and management practices in small rural backyard poultry flocks in New Zealand.

AIM: To obtain baseline data on the management of small non-commercial backyard poultry flocks, in two rural regions of New Zealand, to investigate potential transmission pathways for avian influenza (AI), and to investigate the presence of AI in these flocks. METHODS: During August-October 2006 a questionnaire was sent to 105 farms in the Bay of Plenty and Wairarapa with poultry flocks comprising fewer than 50 chickens, located near wetlands where AI virus had been detected previously in wild ducks. Information was collected on the number and species of poultry reared, opportunities for interaction between wild birds and poultry, farm biosecurity measures, and health status of poultry. Between September and November 2006, blood and tracheal/cloacal swabs were collected from poultry on a subset of 12 high-risk farms in each location. Influenza A-specific antibodies in sera were assayed using ELISA, and positive sera were further tested for the presence of H5 and H7 subtype-specific antibodies, using haemagglutination inhibition (HI) assay. The presence of influenza A virus in swabs was detected using real-time reverse transcriptase-PCR (RRT-PCR). RESULTS: Returned questionnaires were received from 54 farms. Overall, 80% had only chickens, 13% chickens and ducks, and 7% had chickens and other galliform species. Nearly all (96%) kept backyard chickens for personal consumption of eggs, with a small proportion (19%) preparing birds for the table. On surveyed farms wild waterfowl were seen on pastures (70%) and/or farm waterways (46%). Waterfowl were recorded as visiting areas where domestic birds were kept on 31% of farms. Bird litter and manure were composted (94%) or buried (6%) on-farm, as were most (82%) dead birds. During the targeted cross-sectional survey of 24 farms clinical disease was not recorded in any poultry flock. Of 309 chicken sera tested, 11 (3.6%) from five farms across both regions tested positive for influenza A antibodies. In contrast, 16/54 (30%) duck sera from three farms in the Wairarapa were positive. Avian influenza H5 and H7 subtype-specific antibodies were excluded in ELISA positive sera using HI testing, and influenza A virus was not detected using RRT-PCR. CONCLUSIONS: The study confirmed that small backyard poultry flocks located near waterfowl habitats were exposed to non-notifiable low-pathogenic AI viruses. Findings indicate a number of potential risk pathways for the transmission of AI viruses between wild birds and non-commercial poultry, and hence the need for continued surveillance for AI in backyard flocks and wild birds in New Zealand.

Surveillance for highly pathogenic avian influenza in migratory shorebirds at the terminus of the East Asian-Australasian Flyway.

AIM: To determine if migratory birds arriving in New Zealand in the Southern Hemisphere spring of 2004 were infected with the highly pathogenic avian influenza (AI) virus, H5N1. METHODS: Cloacal and faecal samples were collected from migratory red knots following their arrival in New Zealand in October 2004. Two species of resident sympatric birds, wrybill and mallard duck, were sampled prior to, and following, the arrival of migratory birds. RESULTS: No AI viruses were isolated from migratory or resident shorebirds. Non-pathogenic AI viruses were isolated from six resident mallard ducks, comprising the endemic subtypes H4 (n=2), H7 (non-pathogenic), H10, and H11 (n=2). CONCLUSIONS: Highly pathogenic AI H5N1 virus was not detected in migratory shorebirds or sympatric water birds in the Firth of Thames, New Zealand, in 2004-2005, despite the possible proximity of migratory birds to outbreaks of the disease in East Asia in 2004.

An immunohistochemical investigation of the relationship between neuronal nitric oxide synthase, GABA and presympathetic paraventricular neurons in the hypothalamus.

Functional studies suggest that nitric oxide (NO) modulates sympathetic outflow by enhancing synaptic GABAergic function. Furthermore, the paraventricular nucleus of the hypothalamus (PVN), an important site for autonomic and endocrine homeostasis constitutes an important center mediating NO actions on sympathetic outflow. However, the exact anatomical organization of GABA and NO releasing neurons with the PVN neurons that regulate autonomic activity is poorly understood. The present study addressed this by identifying PVN-presympathetic neurons in the rat with the retrograde tracer Fluorogold injected into T2 segment of the spinal cord or herpes simplex virus injected into the adrenal medulla (AM). GABAergic or nitric oxide cell bodies were identified by antibodies directed towards GABA or glutamate decarboxylase (GAD67) enzyme or neuronal nitric oxide synthase. This revealed a population of GABAergic neurons to be synaptically associated with a chain of pre-sympathetic neurons targeting the AM. Furthermore, this GABAergic population is not a cellular source of NO. Within the PVN, the majority of cellular nitric oxide was localized to non-spinally projecting neurons while for the PVN-spinally projecting neuronal pool only a minority of neuron were immunopositive for neuronal nitric oxide synthase. In summary, nitrergic and GABAergic neurons are associated with a hierarchical chain of neurons that regulate autonomic outflow. This anatomical arrangement supports the known function role of a NO-GABA modulation of sympathetic outflow.

Iron storage diseases in birds.

Parenteral iron is toxic to many species but, because the uptake of iron from the diet is regulated in the intestine, acute intoxication is not seen under natural conditions. Chronic ingestion of large amounts of absorbable iron in the diet can lead to the storage of iron in the liver in many species, including humans. The excess iron is stored within hepatocytes as haemosiderin and can be quantitatively assessed by liver biopsy or at necropsy using special stains such as Perls iron stain and/or biochemical tests. Iron may also be found within the Kupffer cells in the liver and the macrophage cells of the spleen especially where concurrent diseases are present such as haemolytic anaemia, septicaemia, neoplasia and starvation. Iron accumulation in the liver, also known as haemosiderosis, may not always be associated with clinical disease although in severe cases hepatic damage may occur. It is probable that concurrent disease conditions are largely responsible for the degree and nature of the pathological changes described in most cases of haemosiderosis. In some human individuals there may be a genetic predisposition to iron storage disease, haemochromatosis, associated with poor regulation of iron uptake across the intestine. In severe cases iron pigment will be found in the liver, spleen, gut wall, kidney and heart with subsequent development of ascites, heart failure and multisystem pathology. Clinical disease associated with accumulation of iron in the liver, and other tissues, has been reported in many species of bird although it is most commonly reported in Indian hill mynas ( Gracula religiosa ) and toucans ( Ramphastos sp ). It is likely that the tolerance to the build up of tissue iron varies in individual species of bird and that the predominant predisposing factors may differ, even within closely related taxonomic groups.

Aspergillosis and other causes of mortality in the stitchbird in New Zealand.

Necropsy findings from natural deaths in free living and captive stitchbirds (Notiomystis cincta) were examined over a 3 yr period (November 1991-94) to establish whether disease was an important factor in translocation failures and captive breeding programs undertaken by the New Zealand Department of Conservation. Fresh and fixed material from seven free-living birds and 11 captive birds were examined and were compared with those of a retrospective study of archival material from captive and wild birds collected over a 13 yr period (1979-91). The causes of death in both the present and retrospective study showed a similar pattern with aspergillosis and aspiration pneumonia being the most significant cause of mortality in captive birds. Aspergillosis was diagnosed as the cause of death in 11 of 31 stitchbirds from Mt Bruce; eight of these deaths occurred in the winter months (June-August). The other causes of death in captive birds included trauma, coccidiosis, and sporadic bacterial infections. Hemosiderosis and airsacculitis were common histological findings in most of the wild and captive stitchbirds examined.

Visceral lesions caused by Yersinia pseudotuberculosis, serotype II, in different species of bird.

The size and distribution of histological lesions was studied in 14 cases of avian pseudotuberculosis using a combination of serotype-specific immunohistochemistry and image analysis. The material was derived from recent and archival cases in six canaries (Serinus canaria), two zebra finches (Poephila guttata), three psittaciformes (a kaka, Nestor meriondalis, one rainbow lorikeet, Trichoglossus mollucanus, and one budgerigar, Melopsittacus undulatus), and three New Zealand wood pigeons (Hemiphaga novaeseelandiae). The disease observed in the passerine species appeared to have an acute clinical course and the bacterial lesions were predominately enteric. In the pigeons and the psittaciformes examined, the clinical course of the disease was more chronic in nature and involved the liver and spleen. A correlation was found between the amount of stainable iron in the liver of affected birds and the area of bacterial lesions. All of the 11 strains of Yersinia pseudotuberculosis isolated from fresh necropsy material were serotype II, as determined using a standard serum agglutination test. Immunohistochemistry indicated the presence of antigen(s) common to serotype II in histological material from confirmed cases and in another three cases where the organism had been cultured but the serotype not specified. The in vitro virulence characteristics and plasmid profiles of Y. pseudotuberculosis isolates were also determined.

The effect of parenteral iron dextran, with or without desferrioxamine, on the development of experimental pseudotuberculosis in the domestic chicken.

The development of disease following oral challenge with Yersinia pseudotuberculosis (serotype II) was compared in four groups of five chickens treated with a combination of 10 mg parenteral iron-dextran, 10 mg of the chelating agent desferrioxamine or 10 mg of dextran, 2 days before infection. The chickens pretreated with iron-dextran, with or without desferrioxamine, developed diarrhoea and were lethargic 2 days following bacterial challenge. Chickens not given iron-dextran showed no clinical signs of disease. Histological examination of selected tissues indicated that chickens pre-treated with iron-dextran had significantly more intestinal lesions, but fewer lesions in the spleen, than chickens in groups not treated with iron-dextran. In contrast to control chickens given iron dextran, but not challenged with bacteria, there was no stainable iron in the livers of chickens challenged with Y. pseudotuberculosis 10 days after an injection of 10 mg of iron-dextran. This suggests that chickens challenged with Y. pseudotuberculosis utilised exogenously administered iron during infection.

The role of wild birds and the environment in the epidemiology of Yersiniae in New Zealand.

A survey was carried out to determine the prevalence of Yersiniae in wild passerines in the lower half of the North island of New Zealand over a period of 12 months. Samples of soil, water and foliage were also collected. Out of a total of 1370 avian samples, only two strains of Y. pseudotuberculosis were isolated and a total of 98 strains of environmental yersiniae were identified, including Y. enterocolitica biotype 1a, Y. frederiksenii, Y. kristensenii and Y. intermedia. No strains of Y. pseudotuberculosis were isolated from 1032 non-avian samples collected, which included 100 samples taken from wild mammals. From the non-avian samples, 51 strains of environmental Yersiniae were identified, of which the relative prevalence of Yersinia enterocolitica, biotype 1a, Y. frederiksenii, Y. kristensenii and Y. intermedia was similar to that in the rural passerines. The prevalence of Yersiniae in soil samples was greater in rural areas than in urban areas of the survey region. In both rural and urban passerine populations, the prevalence of Yersiniae was greater in the winter and early summer than at other times of the year.

A quantitative assessment of haemosiderosis in wild and captive birds using image analysis.

An experimental model of haemosiderosis, using the chicken, was developed to examine the distribution of iron in the liver following an injection of iron dextran and to allow calibration of image analysis readings. Image analysis was used as a tool to quantify the stainable iron present in hepatic tissue obtained from wild and captive birds presented for necropsy. A retrospective study of 180 necropsy cases, representing 40 different species of bird, is described. Statistical evaluation of the amount and distribution of stainable iron in the liver tissue of birds from different taxonomic orders indicated that the concentration of iron measured in liver tissue was significantly different in different species of bird. The results of the study showed that hepatic haemosiderosis is a common histological finding in most avian species examined. Although not necessarily associated with overt liver disease, it is often associated with concurrent malignant and infectious diseases. The presence of excess stainable iron in the liver is probably a reflection of an altered iron metabolism associated with increased turnover of tissue iron. This alteration may occur following starvation or trauma.

Carcinoma with concurrent haemosiderosis in an Australian bittern (Botaurus poidloptilus).

A 15-year-old female bittern was presented for necropsy with a history of weight loss and ascites. There was a large neoplastic mass in the abdominal cavity closely attached to the gizzard with several smaller masses attached to the intestine and involving the liver. Much of the normal liver tissue had been obliterated. Histologically, there were many mitotic figures and in some sections the tumour had an acinar pattern. The overall morphology of the tumour was consistent with a carcinoma. The ovary was normal. There was concurrent hepatic haemosiderosis which was severe. As an incidental finding there were several small and two large cysts in the left and right kidneys.

Mycotic disease in the common New Zealand gecko (Hoplodactylus maculatus).

Two adult female geckoes (Hoplodactylus maculatus) from the National Wildlife Centre, Mt Bruce, Masterton, died within the period of a month and were presented to the Department of Veterinary Pathology and Public Health at Massey University for necropsy. The first gecko had numerous 1-2 mm diameter punctate ulcers of the skin over the ventral and dorsal regions of the body. The second animal had slight discolouration of some of the scales. Skin swabs were taken from each case for culture. There were no other gross lesions apparent at necropsy. Histologically, the only lesions in the first gecko were areas of epidermal and dermal ulceration involving fungi and bacteria. In the second gecko, there was limited inflammation in the skin, but in the lungs there was necrosis of the pulmonary septae and constituent muscle bundles caused by fungi whose septate mycelia extended into adjacent large blood vessels and caused mycotic thrombi; hyphae were also found in the spleen and liver. Paecilomyces sp. septate fungus was recovered from both geckoes and Pseudomonas spp. and a mixed Gram-negative flora were recovered from the cutaneous lesions on culture. The death of the first gecko was considered to be due to widespread ulcerative dermatitis, while that of the second gecko was thought to be due to mycotic pneumonitis and mycotic septicaemia. It is believed that environmental factors, such as cold temperature and high humidity, contributed to a reduction in the immune response in the affected geckoes, with the consequent development of overwhelming fungal infections.

The effects of parenteral iron dextran and/or desferrioxamine on the development of experimental pseudotuberculosis in the domestic chicken (Gallus domesticus).

Abstract The development of disease following oral challenge with Yersinia pseudotuberculosis (serotype 11) was compared in four groups of five birds treated with a parenteral dose of 10 mg iron dextran (Imferon), 10 mg of iron dextran plus 10 mg of the chelating agent desferrioxamine (Desferal), 10 mg of desferrioxamine or 10 mg of dextran 2 days before the experiment. Four groups of two birds received the above treatment regimens but no bacterial challenge. In iron dextran treated birds, oral challenge resulted in faecal shedding for the 10 day duration of the experiment, whereas in those birds which received dextran or desferrioxamine alone, the duration of faecal shedding was significantly less. Serological titres to the lipopolysaccharide antigen of the challenge bacteria were also lower in the groups not pretreated with iron dextran. The birds pretreated with iron dextran had diarrhoea and were clinically unwell 2 days following the initial oral challenge. Birds not given iron dextran showed no clinical signs of disease. Histological examination of five selected areas in the liver, spleen and intestine of each bird indicated that birds in the groups treated with iron dextran prior to bacterial challenge had significantly more intestinal lesions than birds in the groups not treated with iron. In contrast, there were significantly more lesions in the spleens of birds not pretreated with iron dextran. There was no evidence of stainable iron in the livers of birds challenged with Y pseudotuberculosis 10 days after an injection of 10 mg of iron dextran. This is in contrast to birds given iron dextran and no bacteria. It was concluded that pretreatment of birds with iron dextran resulted in more severe clinical disease, prolonged faecal shedding with associated intestinal lesions and higher serological titres to bacterial antigen. The number of lesions in the spleen and liver was not necessarily correlated with the severity of clinical disease, and in all infected birds the hepatic iron levels were significantly lower than in the non-infected control birds 10 days after oral challenge. It seems probable that the chicken has a high requirement for iron during infection with Y pseudotuberculosis and mobilises stored and exogenously supplied iron for tissue repair and immunological function.