Analysis of bovine trigeminal ganglia following infection with bovine herpesvirus 1

Following primary infection of the eye, oral cavity, and/or nasal cavity, bovine herpesvirus 1 (BHV-1) establishes latency in trigeminal ganglionic (TG) neurons. Virus reactivation and spread to other susceptible animals occur after natural or corticosteroid-induced stress. Infection of calves with BHV-1 leads to infiltration of lymphocytes in TG and expression of IFN-gamma (interferon-gamma), even in latently infected calves. During latency, virus antigen and nucleic acid positive non-neural cells were occasionally detected in TG suggesting there is a low level of spontaneous reactivation. Since we could not detect virus in ocular or nasal swabs, these rare cells do not support high levels of productive infection and virus release or they do not support virus production at all. Dexamethasone (DEX) was used to initiate reactivation in latently infected calves. Foci of mononuclear or satellite cells undergoing apoptosis were detected 6h after DEX treatment, as judged by the appearance of TUNEL+ cells (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling). BHV-1 antigen expression was initially detected in lymphocytes and other non-neural cells in latently infected calves following DEX treatment. At 24h after DEX treatment, viral antigen expression and nucleic acid were readily detected in neurons. Our data suggest that persistent lymphocyte infiltration and cytokine expression occur during latency because a low number of cells in TG express BHV-1 proteins. Induction of apoptosis and changes in cytokine expression following DEX treatment correlates with reactivation from latency. We hypothesize that inflammatory infiltration of lymphoid cells in TG plays a role in regulating latency.     

Early epithelial invasion by Salmonella enterica serovar Typhimurium DT104 in the swine ileum

Salmonella enterica serovar Typhimurium is an important intestinal pathogen in swine. This study was performed to document the early cellular invasion of Salmonella serovar Typhimurium in swine ileum. Ileal gut-loops were surgically prepared in ten 4- to 5-week-old mixed-breed pigs and inoculated for 0-60 minutes. Loops were harvested and prepared for both scanning and transmission electron microscopy (SEM and TEM, respectively). Preferential bacterial adherence to microfold cells (M cells) was seen within 5 minutes, and by 10 minutes bacterial invasion of the apical membrane was seen in M cells, goblet cells, and enterocytes. This multicellular invasion was observed throughout the course of infection. In addition, SEM revealed a specific affinity of Salmonella serovar Typhimurium to sites of cell extrusion. Using TEM, bacteria in these areas were focused in the crevices formed by the extruding cell and the adjacent cells and in the cytoplasm immediately beneath the extruding cell. Our results suggest that early cellular invasion by Salmonella serovar Typhimurium is nonspecific and rapid in swine. Furthermore, the combination of SEM and TEM data suggests that Salmonella serovar Typhimurium may use sites of cell extrusion as an additional mechanism for early invasion.     

Population changes in Phytophthora infestans in Taiwan associated with the appearance of resistance to metalaxyl

In recent years, late blight, caused by Phytophthora infestans (Mont) De Bary, has increased in severity in many parts of the world, and this has been associated with migrations which have introduced new, arguably more aggressive, populations of the pathogen. In Taiwan, late blight has been endemic on outdoor tomato crops grown in the highlands since the early 1900s, but recent epidemics have been more damaging. To ascertain the present status of the Taiwanese population of P infestans, 139 isolates of the pathogen collected and maintained by the Asian Vegetable Research and Development Center (AVRDC) were characterized using mating type, metalaxyl sensitivity, allozyme genotype, mitochondrial haplotype and RFLP fingerprinting. Up to 1997, all isolates were found to belong to the old clonal lineage of P infestans (US-1 and variants), but in isolates from 1998 a new genotype appeared, and by 2000 this had apparently completely displaced the old population. This new genotype was an A1 mating type and has the dilocus allozyme genotype 100/100/111, 100/100 for the loci coding for glucose-6-phosphate isomerase and peptidase, respectively. These characters, together with RG57 fingerprinting, indicated that these isolates belonged to the US-11 clonal lineage, a minority (11%) being a previously unreported variant of US-11. Whereas metalaxyl-resistant isolates were not detected in the old population, 96% of the new genotypes proved resistant, with the remainder being intermediate in sensitivity. It may be inferred from this sudden, marked change in the characteristics of the Taiwanese P infestans that a new population of the pathogen was introduced around 1997-98 and that this may well have already been metalaxyl-resistant when it arrived, although a role for in situ selection cannot be excluded.     

Cardiac output measured by lithium dilution, thermodilution, and transesophageal Doppler echocardiography in anesthetized horses

OBJECTIVE: To assess the suitability of lithium dilution as a method for measuring cardiac output in anesthetized horses, compared with thermodilution and transesophageal Doppler echocardiography. ANIMALS: 6 horses (3 Thoroughbreds, 3 crossbreeds). PROCEDURE: Cardiac output was measured in 6 anesthetized horses as lithium dilution cardiac output (LiDCO), thermodilution cardiac output (TDCO), and transesophageal Doppler echocardiographic cardiac output (DopplerCO). For the LiDCO measurements, lithium chloride was administered i.v., and cardiac output was derived from the arterial lithium dilution curve. Sodium nitroprusside, phenylephrine hydrochloride, and dobutamine hydrochloride were used to alter cardiac output. Experiments were divided into 4 periods. During each period, 3 LiDCO measurements, 3 DopplerCO measurements, and 3 sets of 3 TDCO measurements were obtained. RESULTS: 70 comparisons were made between LiDCO, DopplerCO, and triplicate TDCO measurements over a range of 10 to 43 L/min. The mean (+/- SD) of the differences of LiDCO - TDCO was -0.86 +/- 2.80 L/min; LiDCO = -1.90 + 1.05 TDCO (r = 0.94). The mean of the differences of DopplerCO - TDCO was 1.82 +/- 2.67 L/min; DopplerCO = 2.36 + 0.98 TDCO (r = 0.94). The mean of the differences of LiDCO - DopplerCO was -2.68 +/- 3.01 L/min; LiDCO = -2.53 + 0.99 DopplerCO (r = 0.93). CONCLUSIONS AND CLINICAL RELEVANCE: These results indicate that lithium dilution is a suitable method for measuring cardiac output in horses. As well as being accurate, it avoids the need for pulmonary artery catheterization and is quick and safe to use. Monitoring cardiac output during anesthesia in horses may help reduce the high anesthetic mortality in this species.     

Sensitivity and specificity of two serological tests for the detection of ovine paratuberculosis

OBJECTIVE: To determine the sensitivity and specificity of an absorbed ELISA and an AGID test for the detection of clinical and subclinical paratuberculosis in sheep. DESIGN: By testing a panel of sera from 1257 Australian Merino and crossbred sheep greater than 1 year of age, of which 1137 sheep were not infected with Mycobacterium avium subsp paratuberculosis and 120 sheep had paratuberculosis. PROCEDURE: Sera were collected from 457 sheep in Victoria and 800 sheep in Western Australia. Presence of M a paratuberculosis infection in Victorian sheep was determined by histological examination of intestinal tissues, whereas sheep from Western Australia were presumed to be free of Johne's disease. The ability of an absorbed ELISA to discriminate between infected and uninfected sheep was described by test sensitivity and specificity, the distribution of ELISA OD, and the area under a receiver operating characteristic curve. RESULTS: The absorbed ELISA had a specificity of 98.2 to 99.5% (CI) and a sensitivity of 35 to 54% (CI). In sheep from infected flocks in Victoria, the AGID test had a specificity of 99 to 100% (CI) and a sensitivity of 38 to 56% (CI). The sensitivity of serological tests was higher in sheep with a body condition representative of the lower quintile of their flock of origin. CONCLUSION: The AGID test and absorbed ELISA are useful tests for the detection of ovine paratuberculosis. Although the tests had a similar accuracy, they detected different subpopulations of infected sheep with only moderate overlap. The AGID test had a higher specificity than the absorbed ELISA.     

Parasite control methods used by horse owners: factors predisposing to the development of anthelmintic resistance in nematodes

One hundred and fifty horse owners, primarily private owners and riding schools, replied to a questionnaire concerning the practices they used to control parasites. Twenty-seven had experienced a parasite problem. Faecal samples from 188 horses selected at random showed that worm control practices were generally successful; however, many owners were not following recommendations for slowing the development of resistant parasites. In 1996, 86 per cent of the owners were using either three or two classes of anthelmintic a year, and they used a median of six doses with a range from one to 11. Approximately half the owners, more commonly owners of up to five horses, picked up their horses' faeces at least once a week, but these owners also used more doses of anthelmintic a year than owners who did not pick up faeces. One-third of the owners manually removed Gasterophilus species eggs from the horses' hairs, but 94 per cent of them also used ivermectin. Many owners treated specifically for Anoplocephala species, cyathostome larvae and Gasterophilus species, and these owners were the most likely to use three classes of anthelmintic a year. One-hundred-and-seven owners replied to a second questionnaire asking for information about the factors that influenced their anthelmintic control practices. Many owners, particularly private owners, were not influenced by the cost of the anthelmintic. For the timing and frequency of treatment, and the choice of drug, owners were most influenced by advertisements, magazine articles and veterinary surgeons. In two magazines aimed at horse owners, the brands of drugs most frequently advertised were the brands most commonly used by the owners, and articles in the magazines recommended the use of three classes of drug per year. These results are discussed in relation to their influence on the development of anthelmintic-resistant nematodes.     

A cross-sectional study of risk factors for obesity in cats in New Zealand

This study was done to identify risk factors for obesity in an urban cat population in New Zealand. A door-to-door survey (conducted within the city limits of Palmerston North) obtained information on the diet, health and behaviour of 202 cats. One hundred and eighty-two of these cats were weighed and their back and leg lengths were measured. The interviewer's assessment of the body condition of each cat was the dependent variable used in this study. Variables that were identified as significant (p< or =0.1) following univariable analysis were grouped into one of the three models for stepwise logistic multiple regression (one each for cat characteristics, environmental and management variables and feeding variables). A combined logistic-regression analysis was performed on the significant variables identified from the three component models. In the combined model, only three variables were significant: the presence of dogs in a household (decreased odds of obesity), longer leg length and owners underestimating cats' body condition (both increased odds).