Robert J. Callan

Biosecurity and bovine respiratory disease

Although biosecurity practices play a role in minimizing respiratory disease in cattle, they must be used in combination with other management strategies that address the many other risk factors. Because the pathogens involved in bovine respiratory disease are enzootic in the general cattle population, biosecurity practices aimed at the complete elimination of exposure are currently impractical. Several animal husbandry and production management practices can be used to minimize pathogen shedding, exposure, and transmission within a given population, however. Various combinations of these control measures can be applied to individual farms to help decrease the morbidity and mortality attributed to respiratory disease.

Control of bovine viral diarrhea virus in ruminants

Bovine viral diarrhea virus (BVDV) is a diverse group of viruses responsible for causing disease in ruminants worldwide. Since the first description of BVDV as a cause of disease, it has undergone surges and lulls in importance. Epizootics of disease caused by BVDV are described. Although naming of the virus and illness implies gastrointestinal disease in cattle, BVDV is a pathogen that affects multiple organ systems in many animal species. Infection, disease, or both have been described in cattle, sheep, goats, pigs, bison, alpacas, llamas, and white-tailed deer, among others. In 2007, the Office of International Epizootics added bovine viral diarrhea to its list of reportable diseases, but the listing is as a reportable disease of cattle rather than as a reportable disease of multiple species. Although initial descriptions of disease caused by BVDV were of digestive disease, respiratory disease and reproductive losses because of BVDV are the most important economically. BVDV uses multiple strategies to ensure survival and successful propagation in mammalian hosts, and this includes suppression of the host’s immune system, transmission by various direct and indirect routes, and, perhaps most importantly, induction of persistently infected (PI) hosts that shed and transmit BVDV much more efficiently than non-PI animals. Successful control and eventual eradication of BVDV requires a multidimensional approach, involving vaccination, biosecurity, and identification of BVDV reservoirs. The following consensus statement reflects current knowledge and opinion regarding the virus, prevalence and host range, clinical manifestations, and most importantly, the control and potential for ultimate eradication of this important viral pathogen of ruminants.

Prevalence of bovine viral diarrhea virus infections in alpacas in the United States

OBJECTIVE To determine the prevalence of bovine viral diarrhea virus (BVDV)-infected alpaca herds in the United States and investigate factors associated with seropositive herd status and, subsequently, determine the proportion of animals within seropositive alpaca herds that are persistently infected (PI) carriers for BVDV, obtain information regarding previous herd exposure to BVDV, determine titers of anti-BVDV antibodies of dams, and ascertain whether individual seropositive crias had received supplemental colostrum at birth. DESIGN Prevalence study. ANIMALS 63 alpaca herds with >or= 12 registered female alpacas. PROCEDURES 250 alpaca breeders were randomly selected from 562 eligible herds listed in the Alpaca Owner and Breeders Association membership directory and mailed a voluntary participation request. Sixty-three alpaca breeders participated in the study. From each herd, blood samples from >or= 4 crias were tested for BVDV, BVDV RNA, and serum neutralizing antibodies against BVDV. A region of the genome of BVDV recovered from PI crias was sequenced to determine genetic homology. RESULTS Among the 63 herds, 16 (25.4%) had seropositive crias and 4 (6.3%) had PI crias. Infections in 3 of the 4 herds with PI crias were linked as evidence by the genetic homologies of viruses. In addition to PI crias, feeding supplemental colostrum was associated with herd seropositivity. CONCLUSIONS AND CLINICAL RELEVANCE Results confirmed the importance of BVDV infections in alpacas in the United States and highlighted the importance of determining the BVDV infection status of animals before they are commingled to limit exposure of herds to BVDV infection.

Selenium and Vitamin E

Deficiency of selenium and vitamin E has recently been identified as a major health concern of sheep producers in certain regions of the United States, and familiarity with published data on these nutrients seems to be of value to small ruminant practitioners. This article begins with a description of the biochemical roles and metabolism of selenium and vitamin E. A literature review follows in which the influence of these nutrients on the musculoskeletal, reproductive, and immune systems, as well as on flock productivity, is discussed. Methods for detection of deficiency and supplementation strategies are also described.

Occurrence of infectious upper respiratory tract disease and response to vaccination in horses on six sentinel premises in northern Colorado.

REASONS FOR PERFORMING STUDY Horses vaccinated against common agents of infectious upper respiratory disease (IURD) may not have detectable serum antibody and may not be protected from clinical disease. OBJECTIVES The objectives of this study were to 1) investigate the serological response of horses to vaccination against influenza virus (H3N8 and H7N7) and equine herpesviruses (EHV) in a field setting and 2) evaluate associations among vaccination status, serum antibody concentrations, and occurrences of IURD in monitored horses. METHODS In this study, horses on 6 Colorado premises were vaccinated parenterally against influenza virus and EHV, and serological response evaluated. Horses were monitored, and biological samples collected from individuals with clinical IURD and control horses. RESULTS Of 173 horses, 61 (35.3%), 21 (12.1%) and 4 (2.3%) seroconverted in response to vaccination against EHV, influenza virus H7N7 and influenza virus H3N8, respectively. CONCLUSIONS Outbreaks of IURD in study horses were associated with influenza virus H3N8 and Streptococcus equi infection, and serological response to vaccination with conventional products was poor. POTENTIAL RELEVANCE These results confirm that horses may not respond with detectable serological responses to conventional vaccination against common respiratory viruses and, therefore, suggest that alternate methods of protecting horses against common respiratory viruses should be sought.

Malignant Catarrhal Fever: Polymerase Chain Reaction Survey for Ovine Herpesvirus 2 and Other Persistent Herpesvirus and Retrovirus Infections of Dairy Cattle and Bison

Using a polymerase chain reaction (PCR) test for sequences of ovine herpesvirus 2 (OHV2), this virus was shown to be significantly associated with sheep-associated malignant catarrhal fever (SA-MCF) in terminal cases of disease in 34 cattle and 53 bison. Ovine herpesvirus 2 was not detected in cattle (38) and bison (10) that succumbed to other diseases. Other persistent herpesviruses, retroviruses, and pestivirus, some of which have been previously isolated from cases of SA-MCF, were not associated with the disease. These included bovine herpesvirus 4 (BHV4), bovine lymphotrophic herpesvirus (BLHV), bovine syncytial virus (BSV, also known as bovine spumavirus), bovine immunodeficiency virus (BIV), and bovine viral diarrhea virus (BVDV). A PCR survey for OHV2 in DNA from individual cows peripheral blood lymphocytes in 4 dairies showed that the 1 dairy that was in close contact to sheep had a prevalence of OHV2 of 21.3%, whereas the 3 other dairies had no OHV2. Prevalence of the other herpesviruses and retroviruses in the dairy cows was variable, ranging from 2% to 51% for BHV4, 52% to 78.7% for BLHV, and 10% to 34% for BSV Bovine lymphotrophic herpesvirus and BSV were also found in a few (1–4 of 21 tested) cases of terminal SA-MCF, but BIV and BVDV were not found in either the dairy cows sampled, or in the cases of SA-MCF. No significant correlation was found between the presence of any 2 viruses (OHV2, BHV4, BLHV, BSV) in the dairy cows or terminal cases of SA-MCF.

Lack of correlation between antibody titers to fibrinogen-binding protein of Streptococcus equi and persistent carriers of strangles

Previously published studies have neither used nor reported the results of an indirect enzyme-linked immunosorbent assay (iELISA) to measure serologic responses in natural outbreaks of strangles. The concept of using serologic responses to identify persistent carriers of Streptococcus equi has been proposed but not scientifically evaluated. The specific aims of the current study were to determine the duration and level of truncated fibrinogen-binding protein-specific (SeM allele 1) antibody production in ponies involved in a natural outbreak of strangles and to determine if test results from this serologic iELISA could predict persistent carrier status. Serologic samples were obtained before and after an outbreak of naturally occurring strangles infection. Persistent carriers of S. equi were identified via culture and polymerase chain reaction (PCR) testing of lavage fluid collected from the guttural pouches and nasopharynx or swabs of the nasopharynx after recovery from acute disease and at postmortem examination. Logistic regression analysis was used to determine if an association existed between serologic response and persistent carrier state. The ELISA reported in the current study definitively confirmed a recent exposure to S. equi. However, the measured serologic response did not predict carrier status in this strangles outbreak. Therefore, a guttural-pouch endoscopy with subsequent culture or PCR testing to detect S. equi remains the most accurate method available for the identification of persistent carriers.

Acute myeloid leukemia with multilineage dysplasia in an alpaca

An 18-year-old female alpaca was presented to the Colorado State University Veterinary Teaching Hospital for chronic ill thrift over a 1-year period. Six weeks previously, an infected left mandibular cheek tooth was removed by oral extraction. On physical examination the patient was cachectic, lethargic, and weak. Abnormalities on the CBC included neutropenia, thrombocytosis, and severe nonregenerative, macrocytic, hypochromic anemia. Dysplastic nucleated erythrocytes and micromegakaryocytes were observed on the peripheral blood smear. Neutrophils, bands, and metamyelocytes appeared markedly toxic. Numerous blasts containing variable numbers of fine azurophilic granules were also observed. Based on their morphology, the cells were interpreted to be progranulocytes and myeloblasts, and a presumptive diagnosis of acute myeloid leukemia (AML) was made. The blast cells accounted for 60% of the nucleated cell population on bone marrow aspirates, further supporting a diagnosis of AML with multilineage dysplasia. Post mortem examination showed infiltration of the neoplastic cells into spleen, liver, kidney, and lymph nodes. Based on histologic findings, the morphologic diagnoses were disseminated myeloid neoplasia, chronic regionally extensive tooth root abscess, and membranous glomerulonephritis. The neoplastic cells were CD172a-positive on flow cytometry, chloroacetate esterase-positive by cytochemistry, and myeloperoxidase-positive by immunohistochemistry, confirming myeloid origin. To our knowledge, this is the first case of AML with multilineage dysplasia in an alpaca, with only one other case of myelodysplasia described previously in this species.

Alimentary-associated carcinomas in five Vietnamese potbellied pigs

CASE DESCRIPTION 5 Vietnamese potbellied pigs were evaluated for abdominal distress that had not responded to medical treatment (4 pigs) or a draining tract of the cranial abdomen of unknown duration (1 pig). CLINICAL FINDINGS Clinical signs in the pigs included anorexia, vomiting, and constipation. Physical examination revealed a palpable abdominal mass in all pigs. Radiography revealed distended loops of small intestine in 2 pigs. TREATMENT AND OUTCOME 3 pigs were treated successfully with wide-margin excision of the abdominal masses, and 2 were euthanized. Primary tumors were diagnosed at necropsy or through histologic evaluation of biopsy specimens obtained during surgery. Types of tumor included cholangiocellular carcinoma, transmural gastric carcinoma, small intestinal adenocarcinoma, metastatic hepatocellular carcinoma, and carcinoma. The tumors involved the stomach, small intestine, spiral colon, liver, and gall bladder. All 3 surgically treated pigs survived at least 9 months after surgery. CLINICAL RELEVANCE Although rare, neoplasia of the alimentary system should be considered among the differential diagnoses for potbellied pigs with signs of abdominal distress. Wide-margin excision of the neoplastic tissue may result in a good outcome in affected pigs.

Reproductive Techniques in Sheep

This article reviews current methods of evaluating reproductive performance in the sheep industry. The reproductive technologies of breeding soundness examination, reproductive ultrasonography, estrus manipulation, artificial insemination, and embryo transfer are also extensively discussed. The veterinarians current and future role in the application of these technologies is discussed.