New Year's fun findingA 2-year-old female mule deer (Odocoileus hemionus) from western Oklahoma was submitted to the Oklahoma Animal Diseases Diagnostic Laboratory, for necropsy. During examination the following specimens were recovered from the cervical region.  Image 1: Adult nematode recovered from the cervical region of a deer Eleaphora shneideri female (F) and male (M), not associated to the cause of death in this case. (Image 2 and Image 3)
Image 2: Anterior end
Image 3: Posterior end of male nematode with cuticular thickenings (red arrow) and spicules (black arrow) These nematodes are common parasites of mule deer and deer in the US. Adults live in the carotid arteries or their branches; females measure an average of 10 cm and males 7 cm.
E. shneideri are transmitted by Tabanid flies considered cyclodevelopmental hosts. Infective larvae migrate to the leptomeningeal arteries where they develop into young adults and further migrate to the carotid or maxillary arteries where they become adults, releasing microfilariae (average 250 µm in length) into the bloodstream. (Images 4-6). In mule deer E. shneideri is often asymptomatic, in sheep it can cause dermatitis of the head as a reaction to the microfilariae in the skin, also referred as “sore head”. In other atypical hosts such as moose or elk they can develop clinical eleaphorosis, characterized by obstructed blood flow, thrombosis and endothelial damage. Image 4: Microfilaria Image 5: Anterior end of microfilaria Image 6: Posterior end of microfilaria Oinkmas: A piggy Christmas storyA 4-month-old pig was brought for necropsy examination at the Oklahoma Animal Disease Diagnostic Laboratory. The pig had recently died along with 3 other pigs (same age). All had a history of anorexia, low fever and diarrhea. The other 3 pigs had traces of blood on feces. During gross examination, gastritis, enterocolitis and numerous small parasites in the intestine were observed (not recovered). No parasite eggs, oocysts or cysts were recovered during fecal centrifugation from colon content. Histological examination revealed colitis, lymphoplasmacytic, histiocytic, neutrophilic and eosinophilic, with crypt abscess, chronic, moderate and intraepithelial and intraluminal nematodes (Figure 1). Thanks to Drs. Clare Brown and Daniel Barrantes-Murillo for contributing to this case.  Figure 1: A. Intraepithelial and intraluminal nematodes (arrowheads). Hematoxylin and eosin (HE). Bar = 400 mm. B. Transversal sections of intraluminal parasites. BB = bacillary band, C = cuticle, HY = hypodermis, SN = stichosome nucleus. HE. Bar = 60 mm. C. Transversal sections of intraluminal parasite. BB = bacillary band, CA = cuticular annulations, HY = hypodermis, S = stichosome. HE. Bar = 60 mm. D. Transversal sections of intraepithelial parasites. Pseudocoelom (asterisks) and polycytous intestine containing uninucleate epithelial intestinal cells (UI). HE. Bar = 60 mm. E. Transversal sections of intraluminal parasite. Hologenic ovary (O), polymyarian coelomyarian muscle (asterisk) and polycytous intestine containing uninucleate epithelial intestinal cells (UI). HE. Bar = 60 mm. F. The lamina propria is moderately expanded by the infiltration of moderate numbers of lymphocytes, plasma cells, histiocytes and fewer neutrophils and eosinophils, with crypt abscess (asterisk). HE. Bar = 60 mm. Trichuris suis, commonly known as whipworms are trichinellid parasites that live embedded within the epithelial cells of the large intestine, especially the cecum. Severe T. suis infections in young swine cause catarrhal enteritis with diarrhea, anorexia, and retardation of growth. Control of this parasite depends on separating swine from source of infective eggs, while treatment has been successful using Fenbendazole or Dichlorvos. Not what it seems?A 4-month-old shorthair cat was presented to a clinic in Eastern Oklahoma with a history of lethargy and intermittent diarrhea during the past week. Abdominal tenderness was detected at clinical examination. A fecal sample was submitted to the Oklahoma Animal Disease Diagnostic Laboratory and the following was observed on fecal centrifugation with Sheather’s sugar solution (Image 1)  Image 1: Observed on fecal centrifugation with Sheather’s sugar solution Toxocara cati eggs, this nematode parasite infects cats worldwide and can cause visceral larva migrans in humans. T. cati can be transmitted by ingestion of infective eggs, paratenic host and rarely via transmammary when the queen gets acutely infected by the end of the pregnancy. Eggs are dark brown and measure 65 x 75 µm. Occasionally, abnormal forms of helminth eggs are observed and are more often seen in Trichuris vulpis eggs. On this case, black arrows demonstrate the undersize and the triangular shaped egg. Unusual morphology has been associated with early infection, therefore, it is important to recognize the existence of malformed helminth parasite eggs and consider when diagnosing helminth infections. Eerie discoveryA 3-year-old French Bulldog, from Atlanta, GA with no history of travel outside the USA, was presented to a local veterinary clinic due to history of worm expulsion. The dog was on heartworm and flea preventive at the time of clinical exam and lives with 4 more dogs in a fenced backyard that has a small pond. Thank you to Dr. Michelle Cox for referring this case and to Dr. Lindsay Starkey and Rachel Smith (OSU) for submitting it to NCVP. Image 1 & 2: Worms collected Mesocestoides sp. belongs to the class Cestoidea. They can be diagnosed by the presence of mediodorsal genital pores and eggs (30 – 40 µM in diameter, Figure 3) that accumulate in the parauterine organ (Figure 4, black arrowhead).
Mesocestoides sp. infects dogs, cats and wild mammals by ingesting reptiles, amphibians, small mammals or birds containing the infective larval stage called tetrathyridium. The complete life cycle of this parasite has not been fully described but a cysticercoid larval stage preceding the tetrathyridium, is believed to develop in a coprophagic insect. Occasionally Mesocestoides can replicate in the peritoneal cavity of dogs producing anorexia, ascites, vomiting and diarrhea among others. Mesocestoides corti, can multiply asexually in the intestines of dogs. Image. 3: Eggs recovered Image 4: Parauterine organ (black arrow) A sunfish's silent struggleA sunfish (Lepomis spp.) kept in a freshwater aquarium at a zoological collection in Texas was found deceased with bloody lesions across its body. The ~13,000 gallon community aquarium housed sunfish, gar, large-mouth bass, catfish, and turtles, many of which were locally acquired. These small but grossly visible organisms were removed from a section of gill on necropsy and sent to the diagnostic lab for identification. Thanks to Rachel Busselman PhD, DVM Class of 2025 and her supervisor Dr. Gui Verocai DVM, MSc, PhD, DACVM (Parasitology) at Texas A&M for contributing to this case. Images 1 & 2: Several specimens of varying sizes, with dorsal and ventral views Images 3 & 4: Close-ups of ventrum featuring suction cups, either on dissecting microscope (3) or compound microscope at 10x magnification (4). Argulus sp. or fish lice. They are crustacean ectoparasites of fish not uncommonly found to infest freshwater fish. They have a jelly-like appearance, two compound eyes, and a disc-shaped wide carapace covering most of their rounded body. All life stages are parasitic and use a stylet to pierce their fish host, secrete digestive enzymes, and feed on body fluids. Adults are approximately 3-7mm in length and 2-4mm wide and have paired ventral suckers near their mouth to help attach to the fish. Females leave the host to lay rows of eggs on vegetation and hard surfaces in the environment before returning to the host to feed. Infestations on fish can cause local inflammation at sites of attachment, anemia, scale loss, behavior changes (e.g., reduced feeding, rubbing on surfaces), and secondary bacterial infections at the attachment sites. Because of their rapid reproduction rate, infestations can quickly cause morbidity and mortality in captive environments. Argulus spp. can also serve as a mechanical vector or intermediate host for several fish diseases, including spring viremia of carp and several nematode species. Treatment can be challenging and must target each life stage throughout their life cycle, which may take 30 to 60 days. Treatment options include multi-doses of organophosphates, potassium permanganate, or chitin synthesis inhibitors including pesticides such as diflubenzuron. Summer intruder: The chameleon and its unwanted guestA wild-caught, estimated age of 1.5- year-old male panther chameleon (Furcifer pardalis) was brought by the owner to a veterinary clinic in San Diego, California. The owner had noticed worm-like movement under the skin along the lateral coelom in various locations (Image 1). Clinical examination revealed the patient was bright, alert, responsive and in good condition. A blood sample was collected from the right jugular and placed into hematocrit tubes, centrifuged and observed under the microscope. Thanks to Ian Kanda RVT, VTS (Exotics) for providing and sharing this interesting case!
Subsequently a blood smear was performed, and the following was observed. Image 2 and 3 Foleyella furcata, belongs to the family Onchocercidae. It is transmitted by mosquitoes which ingest microfilaria from infected hosts (image 4). In the mosquito they develop into the infective stage and perpetuate the cycle when biting a naïve host. Adults commonly develop in the body fat of chameleons.
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