CVMA | Table of Contents and Abstracts

Table of Contents and AbstractsJuly 2020, Vol. 84, No. 3


Infection of calves with in-vivo passaged bovine parainfluenza-3 virus, alone or in combination with bovine respiratory syncytial virus and bovine coronavirus

John Ellis, Nathan Erickson, Sheryl Gow, Keith West, Stacey Lacoste, Dale Godson (page 163)

Bovine respiratory disease complex is etiologically complex and usually involves co-infection by several agents, including bovine parainfluenza virus-3 (BPIV-3), bovine respiratory syncytial virus (BRSV), and bovine coronavirus (BCoV). Traditionally, vaccines have been tested in seronegative calves infected with a single in vitro-passaged agent, often with little disease, resulting in unvaccinated subjects. To overcome the potential problem of attenuation coincident with in vitro culture of the viruses, cocktails of field isolates of BPIV-3s and BCoVs were passaged in the lungs of neonatal colostrum-deprived calves. Lung lavage fluids were used as inocula, alone and in combination with in-vivo passaged BRSV, and aerosolized into a trailer containing conventionally reared 9-week-old weaned Holstein calves with decayed, but still measurable, maternal antibodies. Calves developed acute respiratory disease of variable severity. Upon necropsy, there were characteristic gross and histologic lesions in the respiratory tract, associated immunohistochemically with BPIV-3, BRSV, and BCoV. In-vivo passage of viruses is an alternative to in vitro culture to produce inocula to better study the pathogenesis of infection and more rigorously and relevantly assess vaccine efficacy.

A modified-live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine protects late-term pregnancy gilts against a heterologous PRRSV-2 challenge

Siyeon Yang, Ikjae Kang, Hyejean Cho, Taehwan Oh, Kee Hwan Park, Kyung-Duk Min, Chanhee Chae (page 172)

The objective of this study was to evaluate the efficacy of a modified-live virus (MLV) porcine reproductive and respiratory syndrome virus (PRRSV) vaccine against a heterologous PRRSV-2 challenge in late-term pregnancy gilts under experimental conditions. Eighteen gilts were randomly assigned to vaccinated-challenged, unvaccinated-challenged, and unvaccinated-unchallenged groups (n = 6 gilts per group). Pregnant gilts in the vaccinated-challenged and unvaccinated-unchallenged groups were able to carry their pregnancies to full term and farrowed after 114 to 115 days of gestation. In contrast, pregnant gilts in the unvaccinated-challenged group did not reach full term and farrowed early, after 104 to 108 days of gestation. Pregnant gilts vaccinated with the PRRSV-2 MLV vaccine exhibited a reduction in PRRSV-2 viremia. At the time of challenge with PRRSV-2, vaccinated gilts had relatively low levels of neutralizing antibody titers (≤ 1:16 titer), whereas the number of interferon-γ-secreting cells (IFN-γ-SC) was consistently at protective levels (IFN-γ-SC, ≥ 150 per million). Induction of cell-mediated immunity, as measured by PRRSV-2-specific IFN-γ-SC, correlated with a reduction in PRRSV-2 viremia. Duration of immunity was a minimum of 19 wk. Taken together, the results presented here suggest that vaccination of gilts with a PRRSV-2 MLV vaccine can protect against a heterologous PRRSV-2 challenge and improve the reproductive performance of late-term pregnancy gilts.

Prevalence of feline herpesvirus-1, feline calicivirus, Chlamydia felis, and Bordetella bronchiseptica in a population of shelter cats on Prince Edward Island

Julie Walter, Peter Foley, Carmencita Yason, Raphael Vanderstichel, Anne Muckle (page 181)

The prevalence of the causative agents of feline upper respiratory tract disease (URTD) has been previously documented in many regions worldwide, but has yet to be reported in eastern Canada. The objectives of this study were to determine the prevalence of feline herpesvirus-1 (FHV-1), feline calicivirus (FCV), Chlamydia felis (C. felis), and Bordetella bronchiseptica (B. bronchiseptica) in a population of shelter cats with clinical signs related to URTD on Prince Edward Island, Canada; to compare the prevalence of FHV-1 and FCV as detected by polymerase chain reaction (PCR) and virus isolation (VI) in this population; and lastly, to determine whether factors, such as co-infections, time of year, concurrent feline leukemia virus (FeLV)- or feline immunodeficiency virus (FIV)-positive status, or clinical signs, were associated with prevalence of particular pathogens. Conjunctival, nasal mucosal, and oropharyngeal swabs were collected from 82 cats with clinical signs consistent with URTD. Samples were pooled in transport medium and PCR was used to detect FHV-1, FCV, and C. felis and VI was also used to detect FHV-1 and FCV. A separate swab was submitted for aerobic bacterial culture to detect B. bronchiseptica. Feline herpesvirus-1 (FHV-1) was the most prevalent in this population, followed by C. felis, B. bronchiseptica, and FCV. Of the 4 cats that were positive for B. bronchiseptica, 3 were concurrently positive for FHV-1. All positive B. bronchiseptica cultures were resistant to cefovecin. The prevalence for FHV-1 was lowest in autumn (seasons P < 0.001) and was positively associated with the presence of nasal discharge (P = 0.018) and coughing (P = 0.043).

Effects of the monoacylglycerol lipase inhibitor JZL184 on chickens infected with avian pathogenic Escherichia coli O78: A preliminary pharmacokinetic and infection study

Cherry P. Ho, Abdolsamad Borazjani, Matthew K. Ross, Chinling Wang (page 189)

The endocannabinoid (eCB) system modulates the degree of injury caused by inflammation, while enhancing the activity of phagocytes that promote resolution of inflammation and tissue repair. In-vitro studies with the monoacylglycerol lipase (MAGL) inhibitor JZL184 have suggested that increased eCB signaling might enhance the ability of the host immune system to clear invading pathogens. Although the neurochemical effects of JZL184 on the eCB system in rodents are well-known, its immune-regulating effects are less clear, especially in chickens. The primary objective of this study was to explore whether modulating the eCB system affects immune responses in chickens. To do this, we administered JZL184 [10 and 40 mg/kg body weight (BW), intraperitoneal injection] into chickens prior to a challenge with avian pathogenic Escherichia coli (APEC) O78. Bacteria were isolated from livers, blood, air sacs, and hearts at 8, 28, and 56 h post-infection and the gross lesions in air sacs, livers, and hearts were also examined. Serum levels of JZL184 were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), which indicated that the drug was distributed systemically. The number of birds positive for airsacculitis after APEC O78 challenge was marginally higher in groups treated with JZL184 than in the control group (P = 0.064). Rather than augmenting host defense and enhancing pathogen clearance, these results suggested that JZL184 might have immunosuppressive effects that exacerbated APEC O78 infection in chickens.

Use of serum amyloid A in serum and synovial fluid to detect eradication of infection in experimental septic arthritis in horses

Seiji Yoshimura, Roman V. Koziy, Ryan Dickinson, Igor Moshynskyy, Joscelyn A. McKenzie, Elemir Simko, José L. Bracamonte (page 198)

While serum amyloid A (SAA) has been investigated as a potential marker for septic arthritis in horses, no study has reported on whether SAA can be used to detect eradication of joint infection. Therefore, the objective of this study was to investigate whether the eradication of joint infection in experimentally induced septic arthritis in horses can be detected using serum and synovial fluid SAA. A total of 17 horses were randomly assigned to 3 groups. A middle carpal joint of each horse was injected with saline (control group, n = 3), lipopolysaccharide (LPS) (nonseptic synovitis group, n = 6), or Escherichia coli (septic arthritis group, n = 8) on day 0. Starting on day 1, horses underwent treatment for septic arthritis. Sequential samples of serum and synovial fluid were collected, and quantification of SAA was carried out. Concentrations of serum and synovial fluid SAA were compared among groups and time points. A concurrent study was conducted and determined that infection was eradicated on day 4 in this experimental model of septic arthritis. Concentrations of serum and synovial fluid SAA rapidly increased after inoculation of E. coli and were highest on day 3 and day 4, respectively. Thereafter, both serum and synovial fluid SAA decreased with eradication of joint infection, although they remained significantly increased from baseline until day 9 and day 10, respectively. Serum and synovial fluid SAA did not increase in the control or nonseptic synovitis group. These findings suggest that serial measurements rather than a single measurement of SAA are required to determine eradication of infection from septic arthritis in horses.

Effect of position on transdiaphragmatic pressure and hemodynamic variables in anesthetized horses

Cori D. Youngblood, David S. Hodgson, Warren L. Beard, Yuqi Song, Punit Prakash, Lindsay V. Heflin (page 205)

Recumbency affects respiratory mechanics and oxygenation in anesthetized horses. Changes in pleural and abdominal pressures that can impair ventilation have not been described in all recumbencies. The objective of this study was to determine the effects of patient positioning on transdiaphragmatic pressure and selected hemodynamic variables. Horses were maintained under total intravenous general anesthesia with nasal oxygen supplementation. Transnasal balloon catheters in the stomach and thoracic esophagus were used to measure intrathoracic and gastric pressures in standing horses and in anesthetized horses positioned in right and left lateral recumbency, dorsal recumbency, reverse Trendelenburg position, and Trendelenburg position. Transdiaphragmatic pressure was calculated as the difference between gastric and intrathoracic pressures. Measurements of oxygen saturation (SpO2), heart rate, systolic, diastolic and mean arterial pressures, and respiratory rate were obtained every 5 minutes. When compared to dorsal recumbency, gastric expiratory pressure is decreased in the standing position. Thoracic expiratory pressure is decreased in standing and reverse Trendelenburg. Transdiaphragmatic expiratory pressure and SpO2 are decreased in Trendelenburg. Heart rate is increased in reverse Trendelenburg. Systolic, diastolic, and mean arterial pressures are decreased in reverse Trendelenburg and increased in left lateral and right lateral recumbency. We found that there is wide variation in respiratory pressures between horses and positions and they are not predictive of associated changes in hemodynamic variables.

Efficacy of afoxolaner plus milbemycin oxime and afoxolaner alone as treatment for sarcoptic mange in naturally infested dogs

Camilo Romero-Núñez, Linda G. Bautista-Gómez, Galia Sheinberg, Alberto Martín-Cordero, Ariadna Flores-Ortega, Rafael Heredia-Cárdenas (page 212)

Sarcoptic mange is a pruritic, contagious, ectoparasitic skin disease that affects mammals, including the domestic dog. The objective of this study was to evaluate and compare the efficacy of afoxolaner plus milbemycin oxime (NexGard Spectra) and afoxolaner alone (NexGard) as treatments for sarcoptic mange in naturally infested dogs. A total of 142 dogs naturally infested with Sarcoptes scabiei was evaluated. The dogs were diagnosed by microscopic examinations of skin scrapings. The dogs were divided into 2 groups: 96 dogs were treated with a combined dosage of 2.50 to 5.36 mg/kg body weight (BW) of afoxolaner and 0.50 to 1.07 mg/kg BW of milbemycin oxime and 46 dogs were treated with 2.50 mg/kg BW of afoxolaner alone. The presence or absence of pruritus and lesions were evaluated using an analogous scale on days 7, 14, 21, 28, and 56 after receiving the treatment. Data obtained were analyzed by Student’s t-test (P ≤ 0.05). The single oral treatment of afoxolaner plus milbemycin oxime resulted in a significant reduction in pruritus of 87.4% at 28 d after treatment (P ≤ 0.05). Resolution of the lesions after treatment was variable, with a significant decrease (P ≤ 0.05) observed within the first 14 d, although this parameter continued to improve until the end of the study on day 28, when a decrease of 96% was observed. By the end of the study, a single dose of either the afoxolaner alone or the afoxolaner combined with milbemycin oxime was effective in significantly reducing the signs associated with sarcoptic mange during a 56-day evaluation period.

A descriptive study of the histopathologic and biochemical liver test abnormalities in dogs with liver disease in Thailand

Sathidpak N. Assawarachan, Phudit Maneesaay, Naris Thengchaisri (page 217)

The present study describes the serum biochemical alterations and histopathological abnormalities in the liver tissue of dogs with liver disease. A survey of hepatic lesions was conducted using ultrasound-guided percutaneous needle biopsies. The hematologic and biochemical changes in dogs with liver lesions were recorded. Chronic hepatitis was the most common liver histopathologic finding (37.9%). Other common findings included liver fibrosis (19.5%), vacuolar hepatopathy (10.3%), cholangiohepatitis (9.2%), hepatocellular carcinoma (4.6%), cholangitis (3.4%), cholangiocarcinoma (2.3%), and congestive hepatopathy (2.3%). Greater than 2-fold elevation of serum alanine aminotransferase (ALT) was a useful indicator, with a sensitivity of 40% to 65% for diagnosing all liver pathologies. Greater than 2-fold elevation of serum alkaline phosphatase (ALP) without significant elevation of ALT was useful for diagnosing liver diseases affected by inflammatory or regressive changes (sensitivity of 40% to 50%). Elevation of ALT, ALP, or a combination of ALT and ALP had a high sensitivity of up to 90% for identifying dogs with liver pathology. Hepatic injury and cholestasis enzymes should be interpreted together with patient history, clinical signs, and liver ultrasonographic appearance before performing a liver biopsy.

Effect of timing of bisphosphonate administration on canine osteosarcoma cells undergoing radiation therapy

Katie Hoddinott, Michelle L. Oblak, Geoffrey A. Wood, Sarah Boston, Anthony J. Mutsaers (page 225)

The effects of radiation therapy may be potentiated by combining radiation therapy with secondary therapies. Clinically, radiation therapy has been combined with bisphosphonates for treatment of canine appendicular osteosarcoma for years. The objective of this study was to determine if the timing of administration of bisphosphonates in relation to radiation therapy alters clonogenic survival or cell viability of canine osteosarcoma cells in vitro. Canine osteosarcoma cells were treated before administration of radiation, concurrent with radiation, or after radiation. Reduction in clonogenic survival was identified when bisphosphonates were administered post-radiation compared with pre-radiation. No significant differences were identified for cell viability at any time points. Further investigation of the cellular effects of bisphosphonates on canine osteosarcoma cells is warranted. Consideration may be given to administering bisphosphonates 24 h after radiation to reduce replication of canine osteosarcoma cells and possibly prolong the analgesic effects of both treatments.

Changes in interferon-gamma and neopterin in female dogs undergoing ovariohysterectomy as elective spay or as treatment of pyometra

Roman Dabrowski, Anna Wdowiak, Marek Szczubial, Leszek Krakowski, Piotr Brodzki, Mariola Bochniarz, Asta Tvarijonaviciute (page 230)

The objective of this study was to determine serum concentrations of interferon-gamma (INF-γ) and neopterin (Np) in dogs with pyometra admitted for surgical treatment and to compare these concentrations to healthy dogs admitted for elective spay. The effects of the surgical procedure were also evaluated by measuring these markers in both groups of dogs before and after ovariohysterectomy. Our study indicates that pre-surgery concentrations of INF-γ (57.4 ± 26.0 pg/mL) and Np (5.6 ± 0.8 nmol/L) in healthy dogs were significantly lower compared to dogs with pyometra (124.3 ± 87.6 pg/mL for INF-γ; 7.0 ± 1.5 nmol/L for Np) (P < 0.05 in both cases). Furthermore, Np was lower in dogs with pyometra 3 days after surgery compared to healthy controls (P < 0.001). During the post-operative period, INF-γ showed no statistically significant changes in any of the groups, while Np showed lower serum concentration on day 3 than on day 0 in the pyometra group (P < 0.001). No statistically significant correlation was detected between serum concentrations of INF-γ and Np. These results indicate that pyometra causes alterations in serum concentrations of INF-γ and Np in female dogs compared to physiological levels before surgery and during the post-operative period.

Brief Communications

Comparative study of the virulence of 3 major Korean porcine circovirus type 2 genotypes (a, b, and d)

Hyejean Cho, Ikjae Kang, Taehwan Oh, Siyeon Yang, Kee Hwan Park, Kyung-Duk Min, Hee Jin Ham, Chanhee Chae (page 235)

The objective of this study was to compare the virulence of 3 major Korean porcine circovirus type 2 (PCV2) genotypes in terms of clinical signs, PCV2 viremia and antibody titers, lymphoid lesions, and PCV2-antigen within lymphoid lesions in experimentally infected pigs. Pigs were infected at 7 weeks with PCV2a, PCV2b, and PCV2d strains and necropsied at 28 days post-infection. No statistical differences were observed in clinical signs, PCV2 viremia and antibody titers, lymphoid lesions scores, and numbers of PCV2 antigens among the 3 major Korean PCV2 genotypes. The results of this study indicate that the 3 major Korean PCV2 genotypes, PCV2a, PCV2b, and PCV2d, have similar virulence.

Protective efficacy of the recombinant lysozyme-PMAP36 fusion protein-inactivated Salmonella Typhimurium vaccine candidate via oral immunization in a murine model

Jayoung Moon, Soyoung Kim, Wonkyong Kim, Zhili Rao, Junghee Park, Byungyong Park, Jin Hur (page 241)

The aim of this study was to evaluate protective efficacy of S. Typhimurium ghost vaccine candidate lysed by the recombinant lysozyme-PMAP36 fusion protein via oral immunization in a murine model. Sixty BALB/c mice were equally divided into 4 groups. Group A mice were inoculated with 20 µL of sterile phosphate-buffered saline (PBS). Groups B-D mice were immunized with approximately 1 × 107, 1 × 108, and 1 × 109 cells of the vaccine candidate, respectively, in 20 µL of PBS. Salmonella-outer-membrane-proteins-specific serum IgG was considerably higher in groups B–D than in group A. The interleukin-10 and interferon-γ levels in groups B–D were significantly higher than in group A. Following challenge with wild-type S. Typhimurium, all immunized groups showed a significant level of protection compared with group A. The highest protection was shown in group D. Overall, these results show that oral immunization with the candidate vaccine can effectively protect mice from S. Typhimurium infection.