Multicenter evaluation of the Vetscan Imagyst system using Ocus 40 and EasyScan One scanners to detect gastrointestinal parasites in feces of dogs and cats

The Vetscan Imagyst system (Zoetis) is a novel, artificial intelligence-driven detection tool that can assist veterinarians in the identification of enteric parasites in dogs and cats. This system consists of a sample preparation device, an automated digital microscope scanner, and a deep-learning algorithm. The EasyScan One scanner (Motic) has had good diagnostic performance compared with manual examinations by experts; however, there are drawbacks when used in veterinary practices in which space for equipment is often limited. To improve the usability of this system, we evaluated an additional scanner, the Ocus 40 (Grundium). Our objectives were to 1) qualitatively evaluate the performance of the Vetscan Imagyst system with the Ocus 40 scanner for identifying Ancylostoma, Toxocara, and Trichuris eggs, Cystoisospora oocysts, and Giardia cysts in canine and feline fecal samples, and 2) expand the assessment of the performance of the Vetscan Imagyst system paired with either the Ocus 40 or EasyScan One scanner to include a larger dataset of 2,191 fecal samples obtained from 4 geographic regions of the United States. When tested with 852 canine and feline fecal samples collected from different geographic regions, the performance of the Vetscan Imagyst system combined with the Ocus 40 scanner was correlated closely with manual evaluations by experts. Sensitivities were 80.0‒97.0% and specificities were 93.7‒100.0% across the targeted parasites. When tested with 1,339 fecal samples, the Vetscan Imagyst system paired with the EasyScan One scanner successfully identified the targeted parasite stages; sensitivities were 73.6‒96.4% and specificities were 79.7‒100.0%.

Survey of zoonotic parasites and bacteria in faeces of Canada geese (Branta canadensis) in North-Central Oklahoma

Background

As a population of non‐migratory Canada geese (Branta canadensis) has been growing in residential and recreational areas, public concerns on potential acquisition of zoonotic pathogens from Canada geese and their faecal deposits have been increasing.

Objectives

The main study objective was to evaluate the prevalence of zoonotic microorganisms, Campylobacter spp., Cryptosporidium spp., Giardia spp. and Salmonella spp. and antimicrobial resistant Escherichia coli in faeces of Canada geese residing in North‐Central Oklahoma, United States.

Methods

A total of 204 faecal samples were collected from 11 locations in North‐Central Oklahoma, where public recreational areas such as lakes and ponds were located, and Canada geese were commonly inhabited. Faecal samples were examined by a centrifugal flotation to evaluate the prevalence of Cryptosporidium spp. and Giardia spp. infections. A total of 180 faecal samples were grouped into 36 pooled samples and cultured using standard culture methods to detect the prevalence of Campylobacter spp. and Salmonella spp. infections. The antimicrobial resistance profile was determined on 32 E. coli isolates recovered from the 36 sample pools, using the Kirby Bauer Disk Diffusion method.

Results

The targeted zoonotic pathogens were not identified by the faecal examinations performed. Of the 32 E. coli isolates, 17 isolates (53.1%) demonstrated resistance to ≥1 antimicrobial agent.

Conclusions

Targeted zoonotic pathogens were not detected among the examined resident Canada geese in North‐Central Oklahoma. The findings of multiple‐antimicrobial resistant E. coli infections are potentially a public health concern although the prevalence was low in this study. Further, larger scale surveys are recommended.

Further evaluation and validation of the VETSCAN IMAGYST: in-clinic feline and canine fecal parasite detection system integrated with a deep learning algorithm

Background

Fecal examinations in pet cats and dogs are key components of routine veterinary practice; however, their accuracy is influenced by diagnostic methodologies and the experience level of personnel performing the tests. The VETSCAN IMAGYST system was developed to provide simpler and easier fecal examinations which are less influenced by examiners’ skills. This system consists of three components: a sample preparation device, an automated microscope scanner, and analysis software. The objectives of this study were to qualitatively evaluate the performance of the VETSCAN IMAGYST system on feline parasites (Ancylostoma and Toxocara cati) and protozoan parasites (Cystoisospora and Giardia) and to assess and compare the performance of the VETSCAN IMAGYST centrifugal flotation method to reference centrifugal and passive flotation methods.

Methods

To evaluate the diagnostic performance of the scanning and algorithmic components of the VETSCAN IMAGYST system, fecal slides were prepared by the VETSCAN IMAGYST centrifugal flotation technique with pre-screened fecal samples collected from dogs and cats and examined by both an algorithm and parasitologists. To assess the performance of the VETSCAN IMAGYST centrifugal flotation technique, diagnostic sensitivity and specificity were calculated and compared to those of conventional flotation techniques.

Results

The performance of the VETSCAN IMAGYST algorithm closely correlated with evaluations by parasitologists, with sensitivity of 75.8–100% and specificity of 93.1-100% across the targeted parasites. For samples with 50 eggs or less per slide, Lin’s concordance correlation coefficients ranged from 0.70 to 0.95 across the targeted parasites. The results of the VETSCAN IMAGYST centrifugal flotation method correlated well with those of the conventional centrifugal flotation method across the targeted parasites: sensitivity of 65.7–100% and specificity of 97.6–100%. Similar results were observed for the conventional passive flotation method compared to the conventional centrifugal flotation method: sensitivity of 56.4–91.7% and specificity of 99.4–100%.

Conclusions

The VETSCAN IMAGYST scanning and algorithmic systems with the VETSCAN IMAGYST fecal preparation technique demonstrated a similar qualitative performance to the parasitologists’ examinations with conventional fecal flotation techniques. Given the deep learning nature of the VETSCAN IMAGYST system, its performance is expected to improve over time, enabling it to be utilized in veterinary clinics to perform fecal examinations accurately and efficiently.

Evaluation of the VETSCAN IMAGYST: an in-clinic canine and feline fecal parasite detection system integrated with a deep learning algorithm

Background

Fecal examination is an important component of routine companion animal wellness exams. Sensitivity and specificity of fecal examinations, however, are influenced by sample preparation methodologies and the level of training and experience of personnel who read fecal slides. The VETSCAN IMAGYST system consists of three components: a sample preparation device, a commercially available scanner, and an analysis software. The VETSCAN IMAGYST automated scanner and cloud-based, deep learning algorithm, locates, classifies, and identifies parasite eggs found on fecal microscopic slides. The main study objectives were (i) to qualitatively evaluate the capabilities of the VETSCAN IMAGYST screening system and (ii) to assess and compare the performance of the VETSCAN IMAGYST fecal preparation methods to conventional fecal flotation techniques.

Methods

To assess the capabilities of VETSCAN IMAGYST screening components, fecal slides were prepared by the VETSCAN IMAGYST centrifugal and passive flotation techniques with 100 pre-screened fecal samples collected from dogs and cats and examined by both the algorithm and parasitologists. To determine the diagnostic sensitivity and specificity of the VETSCAN IMAGYST sample preparation techniques, fecal flotation slides were prepared by four different techniques (VETSCAN IMAGYST centrifugal and passive flotations, conventional centrifugal flotation, and passive flotation using OVASSAY® Plus) and examined by parasitologists. Additionally, required sample preparation and scanning times were estimated on a subset of samples to evaluate VETSCAN IMAGYST ease-of-use.

Results

The algorithm performance of the VETSCAN IMAGYST closely matched that of the parasitologists, with Pearsonʼs correlation coefficient (r) ranging from 0.83–0.99 across four taxa of parasites, Ancylostoma, Toxocara, Trichuris and Taeniidae. Both VETSCAN IMAGYST centrifugal and passive flotation methods correlated well with conventional preparation methods on all targeted parasites (diagnostic sensitivity of 75.8–100%, specificity of 91.8–100%, qualitative agreement between methods of 93.8–94.5%). Sample preparation, slide scan and image analysis were completed within 10–14 min by VETSCAN IMAGYST centrifugal and passive flotations, respectively.

Conclusions

The VETSCAN IMAGYST scanning system with the VETSCAN IMAGYST sample preparation methods demonstrated a qualitative match in comparison to the results of parasitologists’ examinations with conventional fecal flotation techniques. The VETSCAN IMAGYST is an easy-to-use, next generation qualitative and possibly quantitative diagnostic platform that brings expert clinical results into the hands of veterinary clinics.

Retrospective survey of endoparasitism identified in feces of client-owned dogs in North America from 2007 through 2018

Our main study objective was to determine the prevalence and trend of parasitic infection in client-owned dogs examined at the veterinary parasitology diagnostic laboratory of Oklahoma State University over the past 12 years. All results of centrifugal flotation, saline direct smear, sedimentation, Baermann, acid-fast staining for Cryptosporidium detection, and Giardia antigen examinations on fecal samples from client-owned dogs submitted to the Boren Veterinary Medical Hospital and Oklahoma Animal Disease Diagnostic Laboratory of Oklahoma State University from 2007 through 2018 were included. The impact of sex, age, and seasonality on the prevalence of parasitic infection was also statistically evaluated. A total of 7,409 cases were included for this study. Majority of cases (79.58%; 5,896/7,409) did not include any parasites, eggs, larva, oocysts, or cysts. Approximately 15.41% (1,142/7,409) of client-owned dogs were infected by at least one parasite, and 5.01% (371/7,409) of dogs were infected by multiple parasites. The most common parasite stage observed was Ancylostoma eggs (8.23%; 610/7,409), followed by Cystoisospora oocysts (5.02%; 372/7,409), Giardia cysts/antigen (4.06%; 301/7,409), Trichuris vulpis eggs (2.74%; 203/7,409), Toxocara canis eggs (2.54%; 188/7,409), Dipylidium caninum proglottids/egg packets (0.84%; 62/7,409), taeniid proglottids/eggs (0.47%; 35/7,409), Sarcocystis sporocysts (0.38%; 28/7,409), Cryptosporidium oocysts (0.30%; 22/7,409), Strongyloides stercoralis larvae (0.20%; 15/7,409), Alaria eggs (0.19%; 14/7,409), Toxascaris leonina eggs (0.18%; 13/7,409), Capillaria eggs (0.16%; 12/7,409), Hammondia-like small coccidian oocysts (0.16%; 12/7,409), Uncinaria stenocephala eggs (0.13%; 10/7,409), Spirometra eggs (0.09%; 7/7,409), Physaloptera eggs (0.09%; 7/7,409), Heterobilharzia americana eggs (0.08%; 6/7,409), Nanophyetus salmincola eggs (0.08%; 6/7,409), trichomonads (0.08%; 6/7,409), Mesocestoides proglottids/eggs (0.05%; 4/7,409), Baylisascaris eggs (0.01%; 1/7,409), Macracanthorhynchus eggs (0.01%; 1/7,409), and Paragonimus kellicotti eggs (0.01%; 1/7,409). In addition to endoparasites, some ectoparasites, such as Demodex mites (0.22%; 16/7,409), Otodectes cynotis mites (0.01%; 1/7,409), Rhipicephalus sanguineus ticks (0.01%; 1/7,409), and Sarcoptes scabiei mites (0.01%; 1/7,409), were detected by fecal examinations. Pseudo/spurious parasites were identified in approximately 4.35% of cases (322/7,409). There was no statistically significant difference for parasite prevalence between sexes (p = 0.3231). However, statistically significant differences were observed with certain parasites when compared by age groups, and generally, prevalence of parasitism decreased as age of client-owned dogs increased (p < 0.0001). Statistical analyses also revealed significant differences by months (p = 0.0013). Overall, the prevalence of parasitic infection in client-owned dogs decreased over the past 12 years (p < 0.0001).

Prevalence of intestinal parasites in fecal samples and estimation of parasite contamination from dog parks in central Oklahoma

Domestic dogs commonly harbor intestinal parasites in Oklahoma and throughout the world. We tested fecal samples from dog parks to determine the prevalence of intestinal parasites and reported use of parasite control in park-attending dogs and assess potential health risks posed by fecal contamination of public dog parks in this region. Fecal samples (n = 359) were collected from five public access dog parks in central Oklahoma from February to July 2019. Fecal samples were collected immediately after defecation with a corresponding canine lifestyle questionnaire completed by the owner (n = 134) or collected from the ground from unknown animals to assess potential parasitic contamination of the parks (n = 225). Sugar centrifugal flotation and saline sedimentation were performed on all samples for parasite diagnosis. Group comparisons were conducted using the Χ² test and 95% binominal confidence intervals were calculated for each proportion. One or more parasites were identified in 24.0% (86/359) of samples, including 38/134 (28.4%) fresh samples and 48/225 (21.3%) environmental samples; 6.1% were co-infected. Parasites detected included Ancylostoma spp. (14.5%), Trichuris vulpis (6.7%), Cystoisospora spp. (3.6%), Sarcocystis spp. (1.7%), and Giardia duodenalis (1.4%). A small number of samples had Cryptosporidium spp., Toxocara canis, Alaria sp., Taeniidae eggs, or Heterobilharzia americana. Owners reported 73.1% (98/134) of dogs were maintained on heartworm preventive. Intestinal nematodes, but not all parasites, were significantly less commonly detected in dogs reportedly on heartworm preventive (11.2%) compared to dogs not on heartworm preventive (27.8%; P = .0194). These data suggest dogs and people visiting dog parks are at risk of parasite exposure and that an owner-reported history of heartworm preventive use is associated with decreased prevalence of intestinal nematodes.

Retrospective survey of parasitism identified in feces of client-owned cats in North America from 2007 through 2018

Ownership of domestic cats in North America has been on the increase; however, there are only a few surveys conducted on the prevalence of parasitism in client-owned cats over years. Our study objective was to evaluate parasite prevalence through statistical analysis of fecal examination results for client-owned cats on samples submitted to the veterinary parasitology diagnostic laboratory of Oklahoma State University over a 12-year period. All results of centrifugal flotation, saline direct smear, sedimentation, and Baermann examinations on fecal samples submitted to the Boren Veterinary Medical Hospital and Oklahoma Animal Disease Diagnostic Laboratory of Oklahoma State University from 2007 through 2018 were included. The impacts of sex, age, and seasonality on the prevalence of infection were also analyzed. A total of 2586 client-owned cat cases were included for this study. Parasites, eggs, oocysts, larvae, or cysts were not detected in the majority of cases (75.5%; 1,953/2586). Approximately 18.8% (485/2586) of client-owned cats were infected by one parasite, and 5.7% (148/2586) of cats were infected by multiple parasites. The most common parasite stage observed was Cystoisospora oocysts (9.4%; 243/2586), followed by Toxocara cati eggs (7.8%; 202/2586), Giardia cysts (4.0%; 104/2586), Alaria eggs (3.5%; 91/2586), Ancylostoma eggs (1.2%; 32/2586), taeniid proglottids/eggs (1.2%; 30/2586), Dipylidium caninum proglottids/egg packets (1.1 %; 29/2586), and Eucoleus aerophilus eggs (0.7%; 18/2586). Less commonly, Physalopetra eggs (0.19%; 5/2586), Toxascaris leonina eggs (0.19%; 5/2586), Tritrichomonas blagburni trophozoites (0.15%; 4/2586), Ollulanus tricuspis larvae/adults (0.12%; 3/2586), Platynosomum fastosum eggs (0.12%; 3/2586), Aelurostrongylus abstrusus larvae (0.08%; 2/2323), Sarcocystis sporocysts (0.08%; 2/2586), Spirometra eggs (0.08%; 2/2586), Mesocestoides proglottids/eggs (0.08%; 2/2586), Trichuris felis eggs (0.08%; 2/2586), Cryptosporidium oocysts (0.04%; 1/2586), and Toxoplasma-like small coccidian oocysts (0.04%; 1/2586) were detected. Additionally, fecal examinations revealed some ectoparasites: Demodex mites (0.9%; 24/2586), Cheyletiella mites (0.15%; 4/2586), and Otodectes cynotis mites (0.04%; 1/2586). There was no statistical significance between different sex groups (p = 0.3316). Age affected the prevalence of Cystoisospora, T. cati, Giardia, and Alaria infections with prevalence decreasing as age increased (p < 0.0001). Statistical analyses also revealed significant differences by months; the higher prevalence of infection occurred from summer through fall (p = 0.0004). Overall, as the number of submittals increased, the prevalence of infection increased over the last 12 years (p < 0.0001). This study supports continuing the current practice of routine broad-spectrum anthelmintic and ectoparasitic treatments for client-owned cats as well as annual/biannual fecal examination.

Nymphal engorgement weight predicts sex of adult Amblyomma americanum, Amblyomma maculatum, Dermacentor andersoni, Dermacentor variabilis, and Rhipicephalus sanguineus ticks

The engorgement weights of laboratory-raised nymphs of five common ticks in the USA, Amblyomma americanum, Amblyomma maculatum, Dermacentor andersoni, Dermacentor variabilis, and Rhipicephalus sanguineus, experimentally fed to repletion on an adult sheep (Ovis aries) were evaluated to determine the sex of molted adult ticks. Length of feeding period of nymphs, molting success and durations, and sex ratios between tick species were also compared. Individual replete nymphs were weighed and allowed to molt to adults in a humidity chamber. Length of feeding duration was different by species (F_4,7785 = 1963.79; P < 0.0001); R. sanguineus nymphs became replete fastest, followed by A. americanum, D. variabilis, A. maculatum, and D. andersoni. Significant difference in molting success was not detected. The mean body weight of engorged nymphs of A. americanum (t = 32.3; df = 662), A. maculatum (t = - 9.70; df = 255), D. variabilis (t = 15.7; df = 751), and R. sanguineus (t = 5.17; df = 560; all P < 0.0001) molting into females was greater than that of nymphs molting into males, whereas heavier D. andersoni engorged nymphs became males (t = 8.71; df = 480; P < 0.0001). Amblyomma maculatum nymphs that molted to females fed to repletion faster (t = 3.33; df = 265; P ≤ 0.001) than nymphs that molted to males and a higher proportion (χ² = 48.4; df = 1, P < 0.0001) of A. maculatum and D. andersoni (χ² = 8.19; df = 1, P = 0.004) molted to females than males. Our study demonstrated biological and behavioral differences in and between engorging nymphs of five ixodid species. These findings may aid in studies evaluating the role of tick sex in transmission of tick-borne pathogens.

A zoonotic parasite, Linguatula serrata, infection in a dog imported from Ethiopia to the United States

A moderate number of oval-shaped, 114.7 × 61.3 μm in size, amber-colored, arthropod-like eggs that had chitinous, smooth, semi-thickened outer wall and 2-4 short appendages armed with 2 terminal hook-like structures were detected in multiple fecal samples from an approximately 9-month-old, intact female, collie-mixed dog that had been recently imported from Ethiopia to Oklahoma, United States. Initially the unusual arthropod-like eggs were considered to be a pseudoparasite, most likely mite eggs. However, based on the history of the dog, morphology of the eggs, and presence of the eggs in repetitive fecal flotations, a pentastomid, Linguatula serrata, was suspected. DNA extraction and PCR analysis of the partial 18S rRNA gene were performed on the eggs, and nucleic acid sequence showed 100% homology to L. serrata, a parasite of dogs, and L. arctica, a parasite of Norwegian reindeers. Rhinoscopy and head CT scan on the dog failed to demonstrate adult parasites or detect any pathologic changes. At this time, pentastomid eggs were no longer observed on fecal flotation. Due to the possibility of juvenile stages of the parasite still migrating in the dog, fluralaner (Bravecto®, Merck) was administered and continuing treatment recommended for at least 6 months. A follow-up fecal examination conducted a month after the treatment did not reveal any parasites or eggs. This is a case report of canine linguatuliasis diagnosed in Oklahoma, United States.

Fecal survey of parasites in free-roaming cats in northcentral Oklahoma, United States

Cats can be infected by various intestinal parasites, some that are zoonotic. Although surveys of parasite prevalence in owned and shelter cats have been published, none addressed free-roaming, wild-trapped, domestic cat (Felis catus) populations. An opportunity to determine the prevalence of intestinal parasites in wild-trapped, free-roaming cats in northcentral Oklahoma, United States occurred through a trap-neuter-return (TNR) program conducted at Oklahoma State University, Boren Veterinary Medical Hospital, between February 2015 and April 2016. Approximately 1 g to 5 g of feces was collected from 846 free-roaming cats either from cage traps, when available, or rectally using disposable fecal loops and examined by centrifugal fecal flotation tests with 33% zinc sulfate solution. Parasite infections were confirmed by microscopic detection of eggs, cysts, or oocysts and visual detection of proglottids. Approximately 63.9% (541/846) of free-roaming cats were infected by at least one parasite, and 24.9% (211/846) of cats were infected by multiple parasites. The most common intestinal parasite infections detected were: Toxocara cati (44.6%; 377/846), followed by Alaria (13.4%; 113/846), Ancylostoma (11.2%; 95/846), Cystoisospora (9.7%; 82/846), taeniids (7.7%; 65/846), Dipylidium caninum (4.5%; 38/846), Physaloptera (2.2%; 19/846), Eucoleus aerophilus (1.4%; 12/846), Giardia (1.2%; 10/846), and a small (10-12 μm in diameter) Toxoplasma-like oocyst (0.1%; 1/846). A few ectoparasites, Demodex gatoi (0.5%; 4/846) and Cheyletiella (0.1%; 1/846), were also detected by fecal flotation. Our findings indicate that a higher prevalence of parasite infections occurs in free-roaming cats in Oklahoma than in owned cats, and these free-roaming cats contribute to contamination of the environment with several zoonotic parasites. Regional data on the prevalence of parasites in free-roaming cats can aid in the justification for parasite control programs in owned cats since both can share the same environment and supports the current practice of routine broad-spectrum anthelmintic and ectoparasite treatments for owned cats.

Dracunculus infections in domestic dogs and cats in North America; an under-recognized parasite?

We reviewed 62 new cases and 18 published reports of Dracunculus infections in domestic dogs and cats to describe the epidemiology of this parasite in dogs and cats in North America. We collected host and parasite data when available, including age, sex, and breed of dog, nematode location in the host, and any clinical signs at presentation and/or description of the apparent lesion. For dogs, infections were noted in six of the AKC breed groups, but none was reported from the toy group or the miscellaneous breed class. Age of infected dogs ranged from 7 months to 19 years (median 4 years; average 5.3 years), and infection rates were similar in male and female dogs. Most nematodes were associated with the distal extremities, but worms were also found in the chest/thorax, abdomen, head, and flank. Although most infected dogs had a single worm, three dogs had two or more worms that were collected from multiple lesions. Three new cat cases, with similar lesions, presentations and seasonality, were detected in Alabama, North Carolina and Texas. Cases were reported from a wide geographic range throughout eastern North America, during every month of the year, but 72% of infections were diagnosed in the late winter to early spring (December to May). All collected worms were larvigerous females which cannot be identified to species based on morphologic characters. Thus, we attempted to amplify and sequence a portion of the cytochrome c oxidase subunit I (COI) gene for specific identification. Although 13 worms from 12 cases were available, sequences were obtained for only eight worms from seven cases. These eight worms were D. insignis, a common parasite of raccoons (Procyon lotor) and other primarily carnivorous mammals. Female worms are the most likely to be detected in dogs and cats because male worms do not emerge, parasites should be preserved in ethanol for molecular identification. Although this study used convenience sampling of available data, we found that the parasite is widespread throughout the eastern US and Canada and that Dracunculus infections in dogs are more common than is revealed in published literature. However, more research is needed to understand the epidemiology, including transmission route(s), prevalence, and distribution of this parasite.

Prime detection of Dirofilaria immitis: understanding the influence of blocked antigen on heartworm test performance

Detection of circulating antigen of Dirofilaria immitis has been a mainstay of identifying heartworm infection in clinical practice for the past three decades. Several validated commercial antigen tests have very good sensitivity, specificity, and positive predictive values, especially when used in patients for which heartworm infection is likely. In some dogs and cats infected with heartworm, antigen may not be available for detection although present in the patient sample; heat pretreatment of these samples reveals the antigen, changing the false negative to positive. This phenomenon was documented in the literature in the 1980s but subsequently overlooked by the heartworm research community for many years. In this review, we provide a summary of the current understanding of the role of heat reversal in diagnosing heartworm infection. This additional diagnostic step is most important for patients in which heartworm infection is likely, such as dogs or cats in an endemic area with an inconsistent history of heartworm preventive use, or dogs with a prior diagnosis of heartworm infection that were recently treated. To illustrate the concept, we share a summary of results from canine samples tested at the state veterinary diagnostic laboratory in Oklahoma, USA in 2017 by modified Knott test and by commercial antigen test before and after heat treatment of samples; in this sample set, heat treatment changed all D. immitis microfilaria-positive but antigen-negative samples to antigen-positive. Pet dogs with a history of consistent preventive use are unlikely to become positive with heat pretreatment; for that reason, routine pretreatment of all samples tested in a veterinary practice is not recommended. We also review known causes of false negative and false positive results on heartworm antigen tests that, although uncommon, can complicate accurate diagnosis in individual patients. Together, this review provides a primer to aid understanding of strategies that can enhance accurate diagnosis of heartworm infection in veterinary practice and clinical research.

Interspecies Variation in the Susceptibility of a Wild-Derived Colony of Mice to Pinworms (Aspiculuris tetraptera)

Pinworms are common parasites in wild and laboratory rodents. Despite their relative nonpathogenicity in immunocompetent models, pinworm infections add an unwanted variable and may confound some types of research. For this reason, health monitoring programs and biosecurity measures aim to minimize the spread of pinworm infections into colonies free from the organisms. Wild-derived and laboratory strains of mice have shown varied susceptibility to infection with Aspiculuris tetraptera, the most commonly found murine pinworm. In particular, susceptibility is increased in wild-derived mice, young animals, and males. Routine surveillance at our institution revealed pinworm infection (A. tetraptera only) within a colony of multiple, wild-derived species of Mus, although only specific species showed positive results during initial sampling. To assess whether species-associated differences in susceptibility were present, we analyzed fecal egg counts of A. tetraptera in every cage of the colony. Our results revealed significant differences in susceptibility between various species and subspecies of Mus. Egg counts were significantly higher in Mus spicilegus than Mus m. domesticus (WSB/EiJ) and Mus macedonicus. Mus spretus had higher egg counts than M. m. domesticus (WSB/EiJ), M. m. musculus (PWK/PhJ), and M. macedonicus. Egg counts did not differ in regard to age, sex, or number of mice per cage. As wild-derived mouse models continue to compliment research largely based on laboratory strains, it will be important to understand host-parasite interactions and their effects on research, particularly studies evaluating immune responses, behavior, growth, and other physiologic parameters.

Prevalence of Cytauxzoon felis infection in healthy free-roaming cats in north-central Oklahoma and central Iowa

Case summary Cytauxzoonosis is a tick-borne disease of cats, and Oklahoma (OK), USA, is considered an enzootic state. To determine the prevalence of Cytauxzoon felis, blood was collected from free-roaming cats, as they are frequently exposed to tick vectors. Our objective was to determine the prevalence of C felis infection in free-roaming cats in north-central Oklahoma and central Iowa (IA). Infection with C felis was determined using DNA extracted from blood and PCR amplification. Blood was collected from 380 free-roaming cats between January and April in 2014 in OK. DNA from C felis was detected in 3/380 (0.8%; 95% confidential interval [CI] 0.22–2.3%). In IA, 292 blood samples were collected between 2012 and 2014. No C felis-infected cats were detected (0; 95% CI 0–0%).

Relevance and novel information The prevalence of C felis (0.8%) in north-central OK reported herein was lower than the previously reported 3.4% in domestic cats in OK. Our study supports that the prevalence in a given enzootic area can vary by location and from the pool of cats sampled. None of 291 (0%) cats were infected with C felis in central IA. To date, only one case of cytauxzoonosis in a domestic cat has been reported in IA. It is important to monitor cats for C felis infections in northern US states, as geographic distribution of Amblyomma americanum expands northward. As free-roaming cats have more contact with the tick vectors of C felis, this population allows us to monitor the expansion of C felis distribution.

Enzymatic properties of dipeptidyl carboxypeptidase from Bacillus pumilus

Enzymatic properties of dipeptidyl carboxypeptidase (DCP) from Bacillus pumilus were investigated. The enzyme was more active on tri- and tetrapeptides than angiotensin-converting enzyme (ACE) from rabbit lung. The presence of chloride ion is essential for the hydrolysis. The Km value of angiotensin I for the enzyme was 0.119 x 10(-3) M. The enzyme was not inhibited by the mammalian ACE inhibitors lisinopril and enalaprilat. The enzyme is readily inhibited by EDTA but restored by Co2+, Mn2+, and Zn2+. Therefore, it seems to be a zinc-metallo protease.

Purification and some properties of dipeptidyl carboxypeptidase from Bacillus pumilus

An intracellular protease from a bacterium, Bacillus pumilus HL721, was purified about 5000-fold by chromatography with a Q-Sepharose Fast Flow column, TSK-gel HA-1000 glass column, and TSK-gel G3000SWXL column using Bz-Gly-Ala-Pro as a substrate. The enzyme was the most active at pH around 7.5 and stable from 4.5 and 8.0. The enzyme activity was inhibited by Cu2+, EDTA, N-ethylmaleimide, o-phenanthroline, and p-chloromercuribenzoic acid. The molecular weight of the enzyme was 155,000 by gel filtration. The enzyme removed dipeptide from the carboxyl end of some peptides used as substrates. From these results the enzyme seems to be a dipeptidyl carboxypeptidase.