Equine viral arteritis in newborn foals: clinical, pathological, serological, microbiological and immunohistochemical observations.

Clinical, pathological, immunohistochemical, serological and microbiological findings are described for 2 geographically and temporally distinct equine arteritis virus (EAV) epidemics in newborn foals. Outbreak A occurred at a commercial Standardbred breeding facility; Outbreak B began in a group of research animals. Clinical signs were severe and primarily referable to the respiratory tract. Fever and leucopenia and/or thrombocytopenia were observed in foals surviving for more than 24 h. The most common gross pathological findings were limited to the respiratory tract. Common histopathological findings included interstitial pneumonia, lymphocytic arteritis and periarteritis with fibrinoid necrosis of the tunica media. Renal tubular necrosis was noted in 2 foals. Immunoperoxidase histochemistry combined with virus isolation was diagnostic in all cases.

An uncommon intestinal manifestation of feline infectious peritonitis: 26 cases (1986-1993).

OBJECTIVE: To provide information on an uncommon intestinal manifestation of feline infectious peritonitis (FIP). DESIGN: Retrospective case series. ANIMALS: 26 cats with FIP that had apparently solitary mural intestinal lesions. PROCEDURE: Histologic records of cats for which FIP had been diagnosed by examination of the surgical biopsy specimens were reviewed. Slides of tissue samples from cats identified in the histologic record as having had intestinal lesions were reviewed by the investigators, and records of cats that appeared to have had solitary mural intestinal lesions were included in the study. Information including signalment; history; physical examination findings; results of hematologic, serum biochemical, and serologic analyses; findings at surgery; and results of histologic examination of biopsy specimens were retrieved from these records and supplemented by medical records and additional information obtained from veterinarians submitting the biopsy samples. ABC immunoperoxidase staining was used to detect FIP virus antigen in tissues from cats whose records were selected for inclusion in the study. RESULTS: 26 of 156 cats with a histologic diagnosis of FIP had apparently solitary mural intestinal lesions. Predominant clinical signs were diarrhea and vomiting for 3 months or less before biopsy. All cats had a mass, believed to be a neoplasm, in the colon or ileocecocolic junction. Affected intestine was markedly thickened, nodular, firm, and white, with multifocal pyogranulomas extending throughout the wall of the intestine on histologic examination. Associated lymph nodes were large. Results of immunohistochemical staining were positive for FIP virus. Most cats were euthanatized or died within 9 months of histologic results, many with signs of multisystemic FIP. CLINICAL IMPLICATIONS: The apparent focal nature of intestinal lesions at surgery leads to a different clinical picture than usually seen with FIP, and masses often are believed to be neoplasms. Diagnosis of FIP is important to prevent exposure and infection of other cats. Evaluation of the entire abdominal cavity, biopsy of visible lesions as well as surrounding organs, and postmortem examination are recommended.

A factor from Trypanosoma cruzi induces repetitive cytosolic free Ca2+ transients in isolated primary canine cardiac myocytes.

An unusual 120-kDa alkaline peptidase contained in a trypomastigote soluble fraction (TSF) of Trypanosoma cruzi is associated with the induction of repetitive Ca2+ transients and subsequent invasion by the parasite of a number of mammalian cell lines, including tissue culture L6E2 myoblasts (B. A. Burleigh and N. W. Andrews, J. Biol. Chem. 270:5172-5180, 1995; S. N. J. Moreno, J. Silva, A. E. Vercesi, and R. Docampo, J. Exp. Med. 180:1535-1540, 1994; A. Rodríguez, M. G. Rioult, A. Ora, and N. W. Andrews, J. Cell Biol. 129:1263-1273, 1995; I. Tardieux, M. H. Nathanson, and N. W. Andrews, J. Exp. Med. 179:1017-1022, 1994). Using single cell spectrofluorometry and whole-cell patch clamping, we show that TSF produces rapid repetitive cytosolic Ca2+ transients (each associated with cell contraction) in primary cardiac myocytes isolated from dogs. The response of myocytes to TSF was dose dependent in that increasing numbers of cells responded to increasing concentrations of TSF. The TSF-induced Ca2+ transients could be obliterated when TSF was heated or treated with trypsin or the protease inhibitor leupeptin. Aprotinin, pepstatin A, and E-64 did not affect TSF activity. The TSF-induced Ca2+ transients and trypomastigote cell invasion could not be inhibited by alpha (prazosin)- or beta (propanolol)-adrenergic blockers or L-type Ca2+ channel blockers (verapamil, nisoldipine, or cadmium) or by removal of extracellular Ca2+. However, inhibition of pertussis toxin-sensitive G proteins and Ca2+ release from the sarcoplasmic reticulum (with thapsigargin or ryanodine) prevented the TSF-induced Ca2+ transients and cell invasion by trypomastigotes. These data suggested that cardiac myocyte pertussis toxin-sensitive G proteins are associated with the regulation of TSF-induced Ca2+ transients and myocyte invasion by trypomastigotes but are independent of Ca2+ entry into the cytosol via L-type Ca2+ channels. The Ca2+ transients are dependent on release of Ca2+ from sarcoplasmic reticulum Ca2+ stores, but this release is not dependent on extracellular Ca2+ or on the classic model of Ca2+ -induced Ca2+ release in cardiac myocytes. Further, subthreshold depolarizations, together with cell contraction as demonstrated by whole-cell patch clamping, occurred with each Ca2+ transient. However, the depolarizations were of magnitude insufficient to generate an action potential, providing further evidence for a lack of dependence on L-type Ca2+ channels and other voltage-dependent channels (Na+ and K+ channels) in the generation of TSF-induced Ca2+ transients. Our findings suggest that primary canine cardiac myocytes respond to TSF and parasite invasion in ways similar to those of the in vitro cell lines studied to date. Since cardiac myocytes are primary targets for T. cruzi in the vertebrate host, our study indicates that TSF may play a role in the pathogenesis of Chagas' disease in humans.

Evaluation of travel and use as a risk factor for seropositivity to Ehrlichia risticii in horses of New York state.

OBJECTIVES: To determine whether mean annual frequency and destination of equine travel was associated with exposure to Ehrlichia risticii and whether these associations were modified by horses' place of residence. DESIGN: Cross-sectional study. SAMPLE POPULATION: 511 equine operations containing 2,587 horses were visited in New York state from a target population of 39,000 operations. PROCEDURE: Each horse was tested for serum antibodies against E risticii, using indirect fluorescent antibody. Information on the horse's travel history, farm's management practices, and surrounding ecology was obtained by personal interview and resource maps. Statistical analyses were performed on 2 cohorts of animals: all horses enrolled in the study and horses born on the property or that resided at least 4 years on the farm. Three county-based risk regions (RR) were identified by use of cluster analysis. RESULTS: Mean seroprevalence for each of the 3 RR was 2.4 (low risk), 8.5 (moderate risk), and 18.5% (high risk) for cohort 1 and 2.5, 8.0, and 18.4% for cohort 2. Among cohorts 1 and 2, pleasure riding and breeding trips were associated with exposure to E risticii, but horse residence (low, moderate, or high RR) was an effect modifier for these associations. Among cohort 1 and stratifying the analysis according to the RR for the travel destination, trail riding at low RR and trail riding at high RR were associated with exposure. Among cohort 2 and stratifying the analysis according to the RR for the travel destination, breeding trips were associated with exposure, and strong effect modification was present for horse residence (low, moderate, or high RR). CONCLUSIONS: Only certain types of travel to specific RR were associated with higher risk of exposure to E risticii. In many instances, travel was not associated, or was associated, with a reduced risk of exposure.

Cross-sectional evaluation of environmental, host, and management factors associated with risk of seropositivity to Ehrlichia risticii in horses of New York state.

OBJECTIVES: To locate counties within New York state with a high seroprevalence among the equine population, to determine host, management, and environmental factors that were associated with seropositivity to Ehrlichia risticii, and to determine evidence for arthropod- or helminth-mediated transmission of E risticii to horses. DESIGN: Cross-sectional study. SAMPLE POPULATION: A random sample of 3,000 of the 39,000 equine operations in New York state was selected, and 2,587 horses from 511 operations were tested. PROCEDURE: Blood samples were collected from horses and tested for seropositivity, using the indirect fluorescent antibody technique. Data on each horse and each farm's management were obtained by personal interview. The significance of each factor on the risk of seropositivity was evaluated, using mixed-effect logistic regression. RESULTS: The seroprevalence among E risticii-nonvaccinated horses was 7.3%. The county-specific seroprevalence ranged from 0 to 27%, with higher-risk counties located at low elevation. Farms at higher risk for having seropositive horses were located predominately at low elevation with no bodies of water nearby. Risk of seropositivity was associated with time spent in a stall or run-in shed, with frequency of application of fly spray, and, depending on duration of residency at the farm, with frequency of deworming with benzimidazole and pyrantel. Standardbreds were 2 to 3 times more likely to have been exposed, compared with Thoroughbreds. Depending on duration of residency at the farm, male and middle-age horses were at higher risk. Up to 32% of the variance for a horse to test seropositive for E risticii on the logit scale was attributable to farm-level random effects, but the nested social group random effect was not significant. CONCLUSIONS: Arthropods and helminths may have a role in the transmission of this disease. Several management factors may directly or indirectly modify the risk of exposure to E risticii, allowing for the possibility of additional control measures besides traditional vaccination strategies.

Concurrent toxoplasmosis and feline infectious peritonitis in a cat.

A 13-year-old, 4-kg, neutered male Maine coon presented with ascites. Toxoplasma gondii tachyzoites were seen within neutrophils and macrophages, and free within the abdominal fluid. At necropsy, many abdominal organs were positive for feline infectious peritonitis (FIP) antigens using immunohistochemical staining. This apparently is the first report of concurrent toxoplasmosis and FIP in a domestic cat.

Trypanosoma cruzi infection in Walker hounds from Virginia.

Trypanosomiasis has been reported in dogs from Texas, Oklahoma, Louisiana, and South Carolina. We describe the first isolation and characterization of Trypanosoma cruzi from a Walker Hound pup in Virginia that also had postvaccinal distemper. The mother of the pup and 7 of its 8 siblings also were found to be infected with T cruzi, suggesting that the parasite had been transmitted transplacentally or through lactation. Parasitologic, serologic, histologic, and molecular methods were used to establish the diagnosis of T cruzi infection in these dogs. In a serologic survey of 12 dogs (including the sire of the pups) from the area in which the index case occurred, none were found to have antibodies to T cruzi. However, 2 of a further 52 dogs from different areas (to the index case), but in the same county, were seropositive to T cruzi. These findings indicate that canine trypanosomiasis is present in an area of the United States not previously known to be enzootic.

Rotavirus and Cryptosporidium shedding in dairy calf feces and its relationship to colostrum immune transfer.

Twenty Holstein calves received 2 L of colostrum twice within 12 h after birth; the first feeding occurred within 2 h of parturition. The increase in adsorption efficiency was related to the gamma globulin provided in the first colostrum feeding. Absorption efficiency ranged from 2.4 to 46.1%. The number of sheddings of rotavirus and Cryptosporidium by the calves during their first 4 wk of life was associated with serum gamma globulin concentration 24 h after birth and absorption efficiency. Absorption efficiency and body weight combined accounted for 60.4% of the variation in the number of sheddings; heavier calves shed more than lighter calves. During the first 4 wk, calves that shed more frequently gained less weight; weight gain was also associated with serum gamma globulin levels 24 h after birth. Colostrum composition varied between quarters of the same cow. Total protein and gamma globulin content of colostrum from the rear quarters was higher than from the front quarters. The association between number of sheddings and absorption efficiency suggest that calves should not be fed colostrum containing less than 9 g/100 ml of total protein.

Response of calves to exposure with swine influenza virus.

In calves inoculated with live swine influenza virus (SIV) A/sw/IL/75 (H1N1) intranasally, SIV was isolated for 7 days, and respiratory tract disease was observed. Antibody was detected in serum of inoculated calves from postinoculation day 9, and virus-neutralization antibody was demonstrated on postinoculation days 14 and 21. The primary response was low, but readily differentiated from the secondary response after calves were challenge exposed with homologous SIV. Pneumonic lesions were observed at necropsy, and histopathologic changes in airways and lungs were consistently found. Fluorescent staining revealed viral activity in epithelial cells of airways. The virus was transferred to healthy calves housed with inoculated calves.

Epidemiological study of swine influenza virus as a component of the respiratory disease complex of feeder calves.

A survey of 177 paired calf sera collected during the years 1978-1981 showed that 3.4% of the calves had prior experience with swine influenza virus. Six calves positive by the single radial hemolysis test (SRH) were also positive by the virus neutralization test (VN) in chicken embryos, and one calf reacted with all three tests (hemagglutination-inhibition (HI), SRH, and VN). The SRH and HI tests available cannot adequately provide the information necessary in a survey of this sort. The HI test is subject to too many variations to enable the data to be used with any degree of confidence. The SRH test lacks accepted standarization for performing the test with cattle sera. Therefore, the VN test is necessary for confirmatory results.

A single radial hemolysis technique for the measurement of influenza virus antibody in cattle serum.

A single radial hemolysis technique (SRH) was used to measure swine influenza virus antibody in calf serum. Heating at 56 C for 60 minutes was necessary to prevent non-specific hemolysis. A significant association was found between the mean diameter of the hemolysis zone obtained with the SRH test and the geometric mean hemagglutination inhibition (HI) titer in sera of 5 calves inoculated with the virus after treatment with periodate (r = 0.92, P 0.01) and receptor destroying enzyme (r = 0.94, P 0.01). Although the SRH technique is not affected by the presence of non-specific inhibitors it is no more sensitive than the HI test. Some disadvantages of the technique included several biological variables difficult to control.

Influenza virus in ruminants: a review.

The host range and pathology of influenza viruses in ruminants is not yet known. However, based on published results of serological and viral studies the following epidemiological features are documented. Positive serology using the complement-fixation technique has been reported for A2/Japan/305/57, Sw/15, Sw/Shope/58, A/Equi/Prague/57, and B/Johannesburg/59 in the United States and against A and B viruses in Italy. Using the hemagglutination inhibition test, positive findings have been reported for A/PR/8/34, A/equi/Prague, A/Equi2/Lexington, Sw/15, Sw/Shope/58, and B/Johannesburg/59 in the USA against A/PR/8/34, A/FM/1/47, B/Bonn, and B/Roma/1/59 in Italy, and against several strains of A2/H3N2 virus in Rumania, USSR, Nepal, India, and Hungary, even though the single radial hemolysis test is recommended for ruminants. The following influenza viruses have been isolated from cattle: Sw/Shope (H1N1) in Hungary, several strains of H3N2 in the USSR, and two viruses with an unidentified hemagglutinin and a type 2 neuraminidase in Hungary and the USSR. The Russian strain A/calf/Duschambe/55/71 (H3N2) has been recognized as a cattle strain.