Puppy's parasite struggle
A 14-week-old intact female Dalmatian, weighing 14 lbs (6.4 kg) was presented to a clinic in Gonzales, TX for dehydration and lethargy. Intake physical exam revealed ascites, pale mucous membranes, lethargy, and muffled lung sounds. Parvovirus antigen test was not detected in feces, but fecal centrifugal flotation demonstrated Ancylostoma sp. eggs 1+, packed cell volume was 20%, and total protein was 5.2. Patient died within 2 hours of presentation. Examination of stained thin blood films demonstrated the following (Image 1).
Image 1: Stained blood film
Alyssa Barta, DVM student, Oklahoma State University, Class of 2025, and Dr. John Withers. Pecan Grove Veterinary Clinic, Gonzales, TX. July 25, 2023.
Trypanosoma cruzi trypomastigotes, observed in the blood of acutely infected dogs for a short time after infection. Morphological identification can be accomplished based on the presence of a terminal/subterminal kinetoplast that is darkly stained at the posterior end, a centrally located nucleus, an undulating membrane, and a flagellum that runs along the length of the trypomastigote body extending anteriorly beyond the margin of the flagellate. Trypomastigotes range in length from 12 to 30 µm and are often C-shaped (arrow) or J-shaped in fixed preparations.
Despite finding trypomastigotes in this case, diagnosing Chagas disease in dogs is usually accomplished by T. cruzi antibody detection, using immunofluorescence antibody (IFA) tests in chronically infected dogs. Trypanosoma cruzi infected dogs are more likely to have ventricular arrhythmias, combinations of ECG abnormalities, and cardiac troponin I (cTNl) >0.129 ng/mL. Surveys of dogs in T. cruzi endemic areas, showed that infected dogs were significantly younger than negative dogs and the highest prevalence of infection were in non-sporting and toy breed dogs. Odds of T. cruzi infection were 13 times greater among dogs where there was an infected housemate or littermate.
The following specimens were incidentally found during necropsy in the colon of a horse from Oklahoma (Image 1).
Image 1: Nematode found at necropsy
Images 2-4: Asymmetrical eggs, pointed tail and esophageal bulb
Oxyuris equi, are the pinworm parasites found in the colon of horses. Gravid females measure 4 to 15 cm. They migrate down the colon to the rectum through the anus to cement the eggs in the surrounding anal skin. The egg masses are a yellowish fluid with thousands of eggs. The fluid and egg masses dry out causing pruritus and contaminating fomites as well as the environment where the eggs become infective. Eggs are asymmetrical with a single polar plug (Image 2). Adults have a pointed tail (image 3) and an esophageal bulb (Image 4).
A striped skunk (Mephitis mephitis) that had been killed by a vehicle in western Oklahoma was examined as part of an ongoing wildlife health survey. Two nematodes (1cm and 3.5cm in length) that had apparently been dislodged on impact were present on the fur and collected for identification.
Image 1: Nematode visible grossly on foot of skunk
Images 2: Anterior end under 4x objective
Image 3: Anterior end under 10x objective
Image 4: Anterior end under 20x objective
Image 5: Posterior end under 10x objective
Adult Physaloptera spp. are found in the stomach of domestic and wild carnivores. The species P. maxillaris most commonly uses skunks as the definitive host. Identification can be determined based on the presence of morphologic features including the cuticular collar and presence of two triangular pseudolips at the anterior end. The length of the body is covered by a cuticle, and the posterior end is blunted. Male Physaloptera spp. have caudal alae at the posterior end, which is useful to differentiate them from ascarid species. Intermediate hosts of Physaloptera spp. include ground beetles and crickets; other vertebrates, including mammals, amphibians, and reptiles, can serve as paratenic hosts.
A fecal sample collected from a raccoon found dead in a home pool was submitted to the parasitology diagnostic laboratory at OADDL, the sample was submitted due to concerns of zoonosis for the home owner. Fecal centrifugation revealed the following:
Image 1 and 2: Eggs found on fecal centrifugation
Baylisascaris procyonis, the raccoon roundworm that causes visceral larva migrans in a wide range of hosts including humans. The infective larvae tend to invade the central nervous system of paratenic hosts and it can be deadly to small mammals and birds. Hay, straw and other bedding materials contaminated with raccoon feces can be a source of infection. Dogs can be definitive hosts for the adult parasites as well.
More than just allergies...
A one-year old Spanish goat was submitted to the Oklahoma Animal Disease Diagnostic Lab for necropsy examination. As an incidental finding during necropsy, the following (Video) was discovered in the right frontal sinus.
Video 1: Larva recovered at necropsy
Image 1: Posterior spiracles of recovered larva
Oestrus ovis, larva third stage (L3). The nasal botfly, is a small fly ~ 1cm long with vestigial mouthparts. They are active during warmer hours of the day, depositing larvae (L1) in the nostril of sheep. The L1 crawls onto the mucous membrane of the nasal passage remaining there for about 2 weeks, or in arrested stage during the winter. The larva then moves to the frontal sinuses where they reach the L3 stage. After full development, the L3 larva crawl down into the nasal passages and is expelled by the sheep’s sneezing.
O. ovis larvae are not pathogenic, but heavy infestation can cause, nasal discharge, sneezing and partial blockage of the nasal passages. Diagnosis is made by location of the larva on the host and morphology of spiracles. (Image 1) Although these larvae are commonly called the sheep botfly, larvae have been also found in deer, goats, and cattle. There are also reports of horse, dog and human infestation.
A juvenile female rabbit was presented for necropsy at the Veterinary Medical Diagnostic Laboratory, University of Missouri. The rabbit was part of an ongoing case of about 200 rabbits displaying various clinical signs including diarrhea, and observation of Eimeria spp. oocysts during fecal examination. At necropsy, white foci (1-3 mm diameter) on the liver and kidney were observed grossly. The following was observed during histological examination of the liver:
Image 1: Histological liver preparation.
Thanks to Dr. Alexis Carpenter, DVM and pathology resident at the University of Missouri, for providing the histological image and anamnesis of the case.
Hepatic coccidiosis, caused by Eimeria stiedae. Some rabbits are asymptomatic; however, the disease can be fatal, especially in young rabbits. Heavily infected rabbits show signs related to decreased hepatic function and bile duct obstruction. Anorexia, debilitation and diarrhea or constipation can occur. The abdomen might be enlarged, and the animal may be icteric. Infection results from ingesting sporulated oocysts that undergo excystation in the duodenum.
Enlargement of the liver, gall bladder, and bile duct may be seen at necropsy with multi-focal nodules caused by hyperplasia and cystic enlargement of the bile duct epithelium. Various life cycle stages of the organism may be seen histopathologically with oocysts in bile duct lumina.
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