Selenium toxicity in breeding ring-necked pheasants (Phasianus colchicus).

A flock of breeding ring-necked pheasants received feed with a high selenium content. Within 4 days of eating the toxic feed, the rate of egg production began to decrease, and bird aggression increased. Approximately 12% of the hens died within a week. Necropsy of the hens revealed colorless fluid around the heart and a friable, but otherwise normal, liver. The rapid onset of the problem and signs noted at necropsy suggested toxicosis. Based on analysis, the feed contained 9.3 ppm of selenium. Selenium toxicity was consistent with the histologic diagnosis of degenerative cardiomyopathy, vacuolar degeneration of hepatocytes, and centrilobular hepatic necrosis. After 8 days, the toxic feed was removed and replaced with fresh feed. Egg production, which had dropped to 50%, returned to normal within 10 days of feed replacement. Hatchability of eggs laid from days 8 to 14 after delivery of the toxic feed was 35%. Approximately 10% of the chicks that hatched had deformed beaks and abnormal eyes. Many of the chicks that died in the shell had deformities, bringing the total to more than 50% of all embryos that developed. The selenium content of eggs that had no embryonic development was 2.05 ppm. Hatchability of eggs laid from days 21 to 28 after the toxic feed was delivered was almost 80%, which was slightly lower than normal. The selenium content of these eggs was 0.30 ppm. These results show the rapid onset and correction of selenium toxicity and suggest that specific embryologic defects are diagnostic for selenium toxicity.

C-cell carcinoma (medullary thyroid carcinoma) associated with multiple endocrine neoplasms in a ferret (Mustela putorius).

A firm, infiltrative mass was found in the thyroid region of an adult castrated male ferret (Mustela putorius) presenting with vague signs of weight loss, minor inappetence, and decreased activity. Efforts to surgically excise the tissue were unsuccessful, and the animal was euthanatized. Gross and histopathologic evaluation revealed multiple endocrine neoplasms, including C-cell carcinoma, adrenocortical adenoma, pheochromocytoma, and endocrine tumor of the pancreas. This is the first descriptive account of a C-cell carcinoma, also known as medullary thyroid carcinoma, in a ferret, although other endocrine neoplasms in this species have been reported with some frequency. These findings mimic features observed in human multiple endocrine neoplasia syndromes.

Elaeophorosis in bighorn sheep in New Mexico.

Two bighorn sheep (Ovis canadensis) in New Mexico (USA) were found to be naturally infected with Elaeophora schneideri. An adult ram examined in 1997 in the Fra Cristobal Mountains had 26 nematodes in the carotid and iliac arteries, and microfilariae were present in the skin, nasal mucosa, brain, and lungs. This ram was markedly debilitated prior to euthanasia and extensive crusty, scabby lesions were observed on its head. In 1998, a yearling ewe found dead adjacent to Watson Mountain near the Gila Wilderness area was found to have 13 nematodes present in its heart. This is the first report of E. schneideri in bighorn sheep, and we suggest that bighorn sheep are susceptible to E. schneideri infection wherever they coexist with mule deer (Odocoileus hemionus hemionus) and appropriate tabanid vectors.

Serologic survey for hantavirus infection in domestic animals and coyotes from New Mexico and northeastern Arizona.

OBJECTIVE: To determine whether animals had serologic evidence of infection with Sin Nombre virus (SNV). DESIGN: Prospective serosurvey. SAMPLE POPULATION: Serum samples were obtained from 145 cats, 85 dogs, 120 horses, and 24 cattle between April 1993 and August 1994 and 54 coyotes between December 1994 and February 1995. PROCEDURE: Serum samples were analyzed by western immunoblot assays for reaction with SNV nucleocapsid antigen. Samples with reactivity to SNV nucleocapsid proteins were used to probe multiple-antigen blots containing recombinant fusion proteins derived from prototypic hantaviruses. Lung tissue or blood clots were used in nested reverse-transcriptase polymerase chain reaction assays for a 320-nucleotide portion of the SNV G1 gene. RESULTS: Sera from 4 of 145 (2.8%) cats and 4 of 85 (3.5%) dogs had trace reactivity to full-length SNV-encoded nucleocapsid proteins. All samples from horses, cattle, and coyotes were nonreactive. Sera from cats and dogs that had trace IgG-antibody reactivity to nucleocapsid proteins were then tested for IgG-antibody reactivity to nucleocapsid proteins of prototypic hantaviruses. One cat had multiple cross-reactivities with these hantaviruses, consistent with exposure to a hantavirus; however, epitope mapping studies did not support this conclusion. Reverse-transcriptase polymerase chain reaction studies of blood clots or lung tissue from 2 animals that had weak reactivity to SNV failed to amplify any hantavirus sequence. CLINICAL IMPLICATIONS: Domestic animals, particularly dogs and cats, as well as coyotes do not appear to have a major role in the maintenance and transmission of SNV.

Effect of chronic ingestion of tarbush (Flourensia cernua) on ewe lambs.

Efforts to increase livestock utilization of tarbush are being coupled with studies to examine tarbush toxicity. Thirty-eight (19/treatment) ewe lambs were assigned at birth to receive either tarbush or alfalfa (15%, dry matter basis) in a sorghum-based growing ration. Lambs were pen-fed this diet 60 d pre-weaning and 60 d post-weaning. No differences existed between treatments in feed consumption. In the tarbush group, 1 lamb died of unknown causes at 90 d of age, while 3 lambs died between 115 and 120 d of age. There were no deaths in the alfalfa group. Shortly before death, lambs fed tarbush appeared lethargic, disoriented and anorectic. At 122 d of age, 5 lambs were randomly selected from each group. Feces and jugular blood samples were obtained from each lamb before being euthanized and necropsied the following day. All fecal samples were negative for occult blood. Serum gamma glutamyl-transpeptidase (P < 0.001) and aspartate aminotransferase (P < 0.001) activities and platelet counts (P < 0.05) were elevated in lambs fed tarbush, while serum calcium concentrations tended (P < 0.10) to be greater. Histologic examination revealed diffuse liver apoptosis in lambs fed tarbush. These data indicate tarbush leaves cause liver damage when fed for extended periods of time.

Embryonic mortality in Sprague-Dawley rats induced by snakeweed (Gutierrezia microcephala).

Three experiments were conducted to determine the effects of ingested snakeweed foliage (SW) on gestating rat embryos. Mature female Sprague-Dawley rats were paired with male rats and after breeding were randomly allotted to diets containing up to 15% SW. Feeding SW caused a decrease (P < .01) in the percentage of live embryos and markedly increased (P < .01) the percentage of dead or resorbed embryos. Snakeweed decreased (P < .01) feed intake in a dose-dependent manner and caused BW loss (P < .01) compared with control animals. However, decreased feed intake had no effect on gestating embryos. Rats fed the control diet, with intakes restricted to equal the average intake of rats fed SW, and those with ad libitum access to the control diet had similar percentages of live and dead embryos (P > .10). Serum clinical profiles reflected undernutrition (decreased triglycerides and cholesterol; P < .01) and mild toxicosis (elevated blood urea nitrogen, creatinine, and bilirubin; P < .01). Because fluid accumulation was noted in the uterus of several rats fed SW, a uterine weight bioassay was conducted. Snakeweed, fed as 10% of the total diet, decreased (P < .01) uterine weight of immature Sprague-Dawley rats. Ingestion of SW during early gestation caused embryonic mortality that could not be attributed to undernutrition or estrogenicity.

DMBA-induced cytotoxicity in lymphoid and nonlymphoid organs of B6C3F1 mice: relation of cell death to target cell intracellular calcium and DNA damage.

The purpose of these studies was to evaluate the effects of 7,12-dimethylbenz[a]anthracene (DMBA) on intracellular free Ca2+ and DNA fragmentation in lymphoid cells obtained from the spleen, thymus, and Peyer's patches (PPs) of female B6C3F1 mice. Previous studies in our laboratories have shown that DMBA is cytotoxic to these lymphoid organs and that calcium homeostasis may be impaired following DMBA treatment. The results of the present studies show that a daily oral 14-day exposure of mice to DMBA produced a dose-dependent decrease in the number of viable cells recovered from the spleen, PPs, and thymus. Intracellular levels of Ca2+ were elevated in the spleen and PPs of mice receiving 140 mg/kg of DMBA. Extensive DNA fragmentation was detected in cells obtained from the spleen and PPs, as well as from the thymus. The thymus and PPs demonstrated DNA fragmentation at significantly lower doses of DMBA (42 mg/kg) than did the spleen (140 mg/kg). While cells obtained from the thymus did not demonstrate an elevation in Ca2+ produced by DMBA, in vitro exposure of isolated thymocytes to 3-30 microM DMBA for 4 hr produced significant elevation of intracellular Ca2+. A "ladder-like" pattern of DNA fragmentation was seen by agarose gel electrophoresis of DNA obtained from thymus cells treated with DMBA in vitro, suggesting DNA degradation by endonucleases. Collectively, these studies suggest that DMBA produces lymphotoxicity through an apoptosis-like mechanism involving fragmentation of genomic DNA by Ca(2+)-activated enzymes.

Clinical, clinicopathologic, and pathologic features of plague in cats: 119 cases (1977-1988).

The clinical, clinicopathologic, and pathologic features of 119 cases of plague in cats from 1977 to 1988 in New Mexico were reviewed. Fifty-three percent were bubonic, 10% were pneumonic, 8% were septicemic, and 29% with neither buboes nor pneumonia were unclassified (but presumed septicemic). Three quarters of the lymphadenopathy was submandibular, and almost half of this was bilateral. One third of all cats had the triad of lethargy, anorexia, and fever in addition to buboes; one quarter had this triad plus abscesses. The overall mortality rate was 33%, with the greatest risk of death in pneumonic cases. For confirmatory diagnosis with a single laboratory test, fluorescent antibody was most frequently used (39% of cases). Cultures and passive hemagluttination titers were also used for confirmation. Gross and histologic findings depended on the type of plague, with Yersinia pestis organisms visualized in buboes of cats with bubonic plague and in the alveolar spaces and respiratory tubules of cats with pneumonic plague.

Neosporosis-like abortions in a herd of dairy cattle.

Twenty-nine cows from a 240-cow drylot Holstein dairy in north-central New Mexico aborted over a period of approximately 5 months. Nine aborted fetuses were necropsied, and all but 1 of the fetuses were between 5 and 7 months of gestation. Microscopic examination of fetal tissues revealed focal necrotizing encephalitis and nonsuppurative myocarditis in 7 of the 9 fetuses. Additional lesions observed in some fetuses were focal hepatic necrosis, nonsuppurative myositis, focal necrotizing placentitis, focal nonsuppurative pneumonia, and focal nonsuppurative nephritis. A few groups of Neospora caninum-like protozoan organisms were observed adjacent to necrotic foci in the brain of 2 fetuses and in the kidney of a third fetus. No other cause of abortion was detected.

Kochia (Kochia scoparia) toxicosis in cattle: results of four experimental grazing trials.

Four kochia grazing trials were completed over a period of 3 years. Yearling steers were allowed to graze pure stands of irrigated and fertilized kochia (Kochia scoparia) for periods of 14 to 105 days. A total of 116 steers were given kochia as their sole forage. Twenty control steers were allowed to graze native grass pasture, and 20 steers were allowed to graze both native grass and kochia pastures. Steers grazing only kochia lost weight or gained poorly compared with control steers grazing native grass. Steers that grazed both kochia and native grass had intermediate rates of gain. Signs of toxicosis were observed only in steers grazing kochia alone. Considerable variability in the degree of toxicosis was observed from one year to another. Morbidity in the steers grazing only kochia varied from 0% (Trial 4) to 28% (Trial 1), and mortality varied from 0% (Trials 3 and 4) to 10% (Trial 2). The most common signs observed in clinically affected steers were depression, dehydration, weight loss, muscular weakness, photosensitization, ocular discharge, and crusty muzzle. In all 4 trials, significant elevations in serum glutamic oxaloacetic transaminase (GOT) and serum gamma glutamyl transpeptidase (GGT) were observed in steers grazing kochia. In 3 of the 4 trials, significant elevations in serum bilirubin, serum calcium, and serum protein were also observed in kochia-fed steers. Necropsies were performed on 6 of 9 steers that died or were euthanized. The primary pathologic findings were severe chronic nephrosis (5 steers) and degenerative hepatopathy (5 steers).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of four serotests for the detection of Dirofilaria immitis infection in dogs.

Three hundred two dogs were tested with 4 serotests for heartworm antigen (AG) or antibody (AB) and with the Knott test. The 4 serotests evaluated were an enzyme-linked immunosorbent assay (ELISA) for adult heartworm-specific AB (AB-ELISA), a quantitative, indirect immunofluorescent assay (IFA) for adult heartworm-specific AB (AB-IFA), an IFA test for microfilaria (MF)-specific AB (MF-IFA), and an ELISA for adult heartworm AG (AG-ELISA). The presence of heartworms was ascertained in all dogs by necropsy examination. Of 302 dogs, 20 (6.6%) had heartworms in the heart at necropsy. Of infected dogs, 9 (45%) had occult infections. Test sensitivities were 75%, 95%, 70%, and 75% for the AB-ELISA, AB-IFA, MF-IFA, and AG-ELISA, respectively. Test specificities were 85% (AB-ELISA), 77% (AB-IFA), 87% (MF-IFA), and 99% (AG-ELISA). The best agreement between serotest results and necropsy findings was obtained with the AG-ELISA (97%). The 4 serotests detected 86% (AB-ELISA), 100% (AB-IFA), 67% (MF-IFA), and 78% (AG-ELISA) of the dogs with occult heartworm infection. A significant (P less than 0.05) association between intestinal parasitism and positive heartworm test results was found with only AB-IFA. Seemingly, the Knott test, or some other concentration method for detecting circulating MF should be the first heartworm test performed. If the examination for MF is negative, the dog has clinical signs, and radiographic findings are suggestive of occult heartworm infection, then a serotest for adult heartworm AG is recommended.

Five-month oral (diet) toxicity/infectivity study of Bacillus thuringiensis insecticides in sheep.

Bacillus thuringiensis insecticides (Bt) [Dipel (test substance D or Thuricide-HP (test substance T)] were administered in the diet for 5 months to castrated mixed rambouillet/merino sheep (24-34 kg at the beginning of the study) at a dose of 500 mg/kg/day (approximately 10(12) spores per day). No treatment-related effect was seen on weight gain or clinical chemistry parameters nor were significant gross clinical changes observed. Several blood and tissue samples taken just prior to the time the animals were killed or at necropsy were found to be positive for Bt when cultured. Detailed gross and microscopic pathologic examination of the sheep revealed several incidental lesions. However, the only lesion that may have been associated with the treatment was lymphocytic hyperplasia in Peyer's patches seen in the cecum of three sheep and it was not considered to be clinically significant.

Experimental infection of lactating goats with Leptospira interrogans serovars pomona and hardjo.

Pathogenesis of Leptospira interrogans serovars pomona and hardjo was evaluated in 14 lactating goats. Although mild clinical signs of leptospiral infection characterized by pyrexia and reduction in milk yield appeared in some animals, a consistent clinical pattern was not observed in the inoculated animals. The pomona serovar was isolated from the kidney of 1 of the 4 goats inoculated with serovar pomona. The hardjo serovar (strain UI 750) was isolated in the rabbit serum-supplemented bovine albumin polysorbate-80 liquid medium only from the mammary gland of 1 of 4 goats at 13 days after inoculation with serovar hardjo. The positive culture was detected after an 8-month incubation period.

Pneumococcus-induced thrombocytopenia in rabbits.

Thrombocytopenia without other hemostatic changes is the most common coagulopathy associated with sepsis. We studied pneumococcus (PNC)-induced hemostatic changes, including thrombocytopenia, in rabbits. Nonviable PNC or saline solution was injected into rabbits preinfused with chromium 51-labeled platelets or iodine 125-fibrinogen. Blood was serially obtained for determination of platelet counts, 51Cr activity or 125I activity, and fibrinogen and fibrin degradation products. Lung, liver, and spleen tissues were counted for 51Cr or 125I activities per gram of wet tissue. PNC-challenged animals displayed profound thrombocytopenia from 0.5 to 48 hours with the mean nadir (-80% relative to the baseline) at 3 hours and a significantly (P less than 0.025) shortened 51Cr-platelet survival of 1.45 +/- 0.71 days vs. 2.72 +/- 1.09 days for saline-injected controls. Circulating fibrinogen level increased, whereas 125I-fibrinogen survival was unchanged (2.6 +/- 0.5 days in PNC-challenged vs. 2.8 +/- 1.0 days in saline-injected). No increased tissue deposition of either 51Cr-labeled platelets or 125I-fibrinogen was found. Rabbits infused with either serum, plasma, or saline solution after each was incubated with PNC all developed significant thrombocytopenia of less than 1 hour duration with maximal mean decreases relative to the baseline of -76% (P less than 0.001), -65% (P less than 0.0005), and -84% (P less than 0.0005), respectively. Inactivation of serum or plasma complement before PNC incubation or heat treatment after PNC incubation in serum or saline solution did not alter the thrombocytopenia. The thrombocytopenia-promoting activity was also trypsin resistant, did not require the presence of serum, plasma, or PNC capsular polysaccharide for its in vitro generation, and had a mol wt of 100,000 to 300,000. Therefore, PNC-induced thrombocytopenia, in the absence of other hemostatic changes, may be explained on the basis of the direct action of a PNC-derived substance(s) on circulating platelets.

Ovine caseous lymphadenitis: disease prevalence, lesion distribution, and thoracic manifestations in a population of mature culled sheep from western United States.

The prevalence, distribution, and severity of caseous lymphadenitis (CLA) lesions in 4,089 mature culled sheep were determined from a sample obtained by random selection of animal lots from a total population of 37,383 animals presented at an abattoir. The animals originated from 5 geographic regions comprising 9 western states. The prevalence rate for all forms of CLA was 42.41%. The prevalence of CLA lesions was significantly different in animals originating from 2 regions than it was in animals from the other 3 regions. The results indicate that CLA is a disease affecting a considerable number of mature culled sheep in different regions of western United States. Lesion distribution was catalogued according to a 4-compartment system: thoracic lymph nodes, lung parenchyma, abdominal tissues, and skeletal tissues including peripheral lymphatic tissues. Prevalence rates were determined for lesions occurring in the thoracic viscera (24.97%), skeletal tissues (23.09%), and abdominal viscera (11.79%). The prevalences of thoracic CLA lesions were significantly different for animals originating from 2 regions than for animals originating from the 3 other regions. Severe or advanced lesions were observed in the thoracic (3.74%) and abdominal viscera (1.27%). Involvements of CLA in the thoracic cavity occurred as abscesses of lung parenchyma, thoracic lymph nodes, or both. The bronchial and mediastinal lymph nodes were the most frequently affected thoracic lymph nodes. The liver was the most frequently affected abdominal organ, with the kidney being the next most commonly affected. The gross and histopathologic characteristics of CLA abscesses and tissues adjacent to the lesions were described.

Pneumococcal sonicate-induced biphasic granulocytopenia and its dissociation from pulmonary leukostasis. The contribution of pneumococcal products and complement to early and late granulocytopenic phases.

The pathogenesis of pneumococcus (PNC)-induced granulocytopenia is unclear. We studied its relationship to pulmonary leukostasis and the possible roles of PNC constituents and complement. Nonviable PNC was infused into normal and 99% C3-depleted rabbits. PNC challenge induced both granulocytopenia and pulmonary leukostasis in normal animals; complement-depleted animals displayed granulocytopenia without pulmonary leukostasis. Therefore an intact complement system was not essential to the granulocytopenia, whereas pulmonary leukostasis was complement-dependent. Rabbits infused with serum, plasma, or nonpyrogenic normal saline, each after in vitro incubation with PNC, developed significant granulocytopenia (p less than 0.001, p less than 0.01, and p less than 0.001, respectively) with maximal mean percent decreases of -98%, -97%, and -91%, respectively. When the animals were sacrificed at 3 hr, no pulmonary leukostasis was found. The granulocytopenia persisted for 3 hr after infusion of either PNC-exposed serum or plasma, whereas the granulocytopenia induced by PNC-exposed saline was of less than or equal to 1 hr duration. If serum or plasma complement was inactivated prior to PNC incubation, subsequent infusion also induced significant granulocytopenia of less than 1 hr duration (p less than 0.05 and p less than 0.01). PNC-exposed saline that was subsequently heat-treated induced this same early (less than or equal to 1 hr) granulocytopenia (p less than 0.05). Control animals infused with serum, plasma, or saline unexposed to PNC displayed neither granulocytopenia nor pulmonary leukostasis. Therefore neither prior in vitro complement inactivation nor heat treatment after PNC incubation prevented the early granulocytopenic phase; in vitro complement inactivation totally aborted the late phase. The complement-independent, heat-stable early granulocytopenic phase was further investigated. Its granulocytopenia-inducing activity did not require the presence of PNC capsular polysaccharide and was resistant to trypsin treatment. With ultrafiltration, its molecular weight was 100,000 to 300,000. Thus PNC-induced granulocytopenia is a multifactorial phenomenon involving both complement-dependent and complement-independent mechanisms as well as contribution by PNC constituents or by-products.