NVCP Case of the Month Flashcards
A five-year-old intact male coonhound presented with weight loss, lethargy, and bloody diarrhea. On physical examination, abdominal pain was evident. Laboratory tests revealed hypoalbuminemia, hyperglobulinemia, hypercalcemia, and nonregenerative anemia. These parasite eggs were found on fecal sedimentation. What are they?
This is Heterobilharzia americana, a digenean trematode that causes canine schistomiasis in the southeastern United States. Normally a parasite of raccoons, dogs are readily infected when they wade or swim in water with active cercaria. Infection can lead to development of a severe, potentially fatal enteritis associated with the movement of the eggs from the mesenteric venules to the intestinal lumen. Treatment requires high-dose praziquantel or fenbendazole, but is not rewarding in all cases. The prognosis in severely affected dogs can be poor.
A 7-month-old steer from southern California passed a number of small rectangular proglottids in his feces. When crushed and examined microscopically, each proglottid was found to contain a number of egg clusters, with each egg containing a set of six distinct hooks. What parasite is this?
This is Wyominia tetoni, a tapeworm of mountain sheep in the western United States that occasionally infects cattle. Effective treatments would be expected to be similar to those that are used for Moneizia sp. infections in cattle.
A seven-year-old Quarter Horse presented with head shaking and obvious duress. Examination of the ears under sedation revealed these organisms. What is this parasite?
Otobius megnini, the spinose ear tick, is found in the ears of horses, cattle, dogs, cats, and occasionally people in the southwestern United States. These soft ticks are readily recognized by the presence of prominent spines on the cuticle, which are understandably irritating to the host. In severe infestations, neurologic signs may result. Only the larval and nymphal stages are parasitic; adults are free-living in the environment.
A fecal sample was submitted from an adult female cat in Oklahoma as part of a routine annual wellness examination. This organism was found on fecal float. What parasite is this?
The feline whipworm, Trichuris felis, referred to by some authors as Trichuris campanula, is considered rare in cats in the continental United States other than occasional cases reported from southern Florida. Further discussions with the owner of this cat revealed she had recently moved with her cat to Oklahoma from the Caribbean. Looks like the cat and owner weren’t the only animals that moved! Although nothing is labeled to treat this parasite in cats in the US, something labeled as effective for whipworms in dogs, such as fenbendazole, milbemycin, or topical moxidectin would be expected to be effective.
A five-year-old spayed female Great Pyrenees presented with profound lethargy. Blood work revealed severe anemia, with a packed cell volume of 8%. The dog was covered with all the different stages of these organisms. What is this most likely to be?
This is Rhipicephalus sanguineus, the brown dog tick. Because this tick can infest kennels and homes, dogs may experience overwhelming infestations that result in anemia and even death due to exsanguination.
A labrador mixed breed dog was diagnosed with ehrlichiosis based on serology but did not respond to doxycycline treatment. Examination of blood smears revealed these organisms. What parasite is this?
This is Hepatozoon americanum, the agent of American canine hepatozoonosis. Dogs become infected when they ingest an infected tick containing sporulated oocysts or a transport host, such as a rabbit or rodent, harboring cystozoites. Dogs with hepatozoonosis require aggressive antiprotozoal therapy and do not respond to doxycycline treatment.
Several of these organisms were recovered from a Quarter horse in New Jersey. What are they and what pathogens do they transmit?
These are Ixodes scapularis, the deer tick or black-legged tick. Adult deer ticks are commonly found on horses, particularly in the colder months, and in areas where disease is endemic, these ticks may transmit Borrelia burgdorferi and Anaplasma phagocytophilum to horses.
Two mixed-breed stray puppies were taken to a veterinary clinic for care. The puppies were heavily infested with ectoparasites including Pulex irritans (human flea) and Rhipicephalus sanguineus (brown dog tick). Bloodwork revealed anemia and this pathogen was seen on a stained blood smear. What is it?
This is Anaplasma platys, a tick-borne bacteria that infects the platelets of dogs and is the causative agent of infectious canine cyclic thrombocytopenia. It can be found worldwide and is presumed to be transmitted via the bite of R. sanguineus in the United States. Because the organisms are often confused with platelet granules, many clinical pathologists prefer to confirm the diagnosis with PCR.
A goat kid developed severe, watery diarrhea. These organisms are found on fecal flotation. What are they?
This is an Eimeria sp. oocyst, a common diarrheal agent in small ruminants. To prevent clinical disease due to coccidiosis, goats are often fed coccidiostats.
These eggs were found on fecal float from a llama. What are they?
These are eggs of Nematodirus sp., a trichostrongylid nematode that is commonly present in cattle, small ruminants, and camelids. Adults of Nematodirus live in the small intestine. Eggs deposited into the environment hatch to release larvae which, upon molting to the third stage, are infective to the next host.
This is the anterior end of a nematode parasite found embedded in a serpiginous pattern in the mucosa of the esophagus and non-glandular stomach of a 32-year-old castrated donkey at necropsy. What is it?
This is Gongylonema, a spirurid nematode acquired by ingestion of dung beetles. The nematode is readily identified by the prominent cuticular bosses as well as the characteristic zigzag pattern it makes in the mucosa of infected animals
This egg was recovered in a fecal flotation from a parrot. What is it?
This is a capillarid egg. Capillarid eggs are morphologically similar to whipworm (Trichuris spp.) eggs in that they are oblong and “barrel-shaped” with bipolar plugs. However, capillarid eggs typically have plugs that are asymmetrical about the straight-line access, and have an ornamental (e.g. pitted or roughened) surface. In birds, capillarid species parasitize different regions of the gastrointestinal tract including the esophagus, crop, and small intestine.
These eggs (averaging 98-134 x 62-68 µm) were found in the feces of a litter of kittens taken to an animal shelter. What are they?
These are eggs of Alaria sp., a trematode of dogs, cats, and various wild carnivores. The life cycle of this fluke involves an aquatic snail first intermediate host and a frog second intermediate host. Mammal, snake, and bird paratenic hosts can also be involved in transmission. Additionally, transmammary transmission in cats has been reported. These eggs are best recovered by fecal sedimentation procedures, but may occasionally be detected in fecal flotations.
This hair was plucked from a laboratory rat in a colony used to study animal behavior. What type of insect is present?
This is an anopluran or sucking louse (Polyplax sp.). Lice are host-specific and complete their entire life cycle on the host; transmission is by direct contact between hosts. The heads of anoplurans, designed to suck blood, are typically narrower than the thorax and have protruding mouthparts. Attached to the hair shaft shown here are louse eggs or nits. In heavy infestations, some anoplurans, including Polyplax sp., can cause anemia.
A one-year-old spayed female black lab was adopted from a shelter/rescue in Tulsa, Okla., 6 months previously. The dog was current on all vaccinations and tested negative for heartworm antigen at the time of adoption. The owner presented the dog because she was pawing at her eye. The dog was not current on heartworm prevention at the time of examination. Mild sedation and close inspection exposed the source of irritation. Excision of the worm from the conjunctival sac revealed it was a female approximately 11.4 cm in length.
These are first-stage larvae of Dracunculus insignis. The long-thin tails of the larvae are distinctive. Normally found in subcutaneous connective tissue of limbs, D. insignis females can occasionally be found in the conjunctiva, heart, vertebral column, and scrotum.
A fecal flotation was performed on a 2-year-old intact Brangus PBR bucking bull dewormed with ivermectin two weeks prior. Identify the egg recovered.
This is a Moniezia sp. egg. Moniezia spp. are cestodes transmitted to ruminants via the ingestion of infected orbatid mites on pasture while grazing. Adults of Moniezia spp. are found in the small intestines of ruminant hosts . Although these tapeworms can become quite long, they are not thought to cause much pathology, unless present in very large numbers.
A 5-year-old cat that was housed in a long-term, limited-access shelter developed scaling and hair loss on the head, pinnae, and shoulder. The cat was observed to groom the affected areas frequently.
This is Demodex gatoi, a cause of demodicosis associated with superficial skin lesions in cats. Identification of demodecosis is often made when ingested mites are recovered on fecal flotation. Because D. gatoi tends to establish as a superficial infestation, fecal float can be useful to confirm the presence of mites, particularly when skin scrapes are unrewarding.
These eggs were passed by a Newfoundland dog. When examined microscopically, the eggs were found to be very much alive. What parasite is this?
This is Mesocestoides, a cyclophyllidean tapeworm of dogs. The life cycle of Mesocestoidesis not fully understood but is thought to involve vertebrate intermediate hosts.
A four-year-old horse presented with severe scoliosis of the cervical vertebrae. Treatment was not attempted and necropsy was performed. Histologic examination of the cervical spinal cord revealed cross-sections of nematodes at the level of the curvature.
These are most likely cross-sections of Parelaphostrongylus tenuis. White-tailed deer are considered the definitive host for P. tenuis. This metastrongylid occasionally infects abnormal hosts including horses, sheep, alpacas, and goats among others. Infections of P. tenuis in horses were first reported in 2004 and a few additional cases have been recognized since.
Five fish from a new shipment of freshwater aquarium fish received by the Tulsa Zoo and Museum died while in quarantine. The fish had white spots on the skin. Multifocal erosive epidermitis with intralesional bacteria and associated protozoa were observed. Sepsis secondary to epidermal damage from the protozoan was believed to be the cause of death in the fish. A sample of a white spot from one of the fish was swabbed onto a slide, fixed, and Romanowsky stained.
The morphological appearance of the protozoan appears very similar to that of Oodinium sp., which is a dinoflagellate that can cause velvety whitish or gold patches on the bodies, fins, and gills of freshwater aquarium fish. Over time, affected fish will have the appearance of being coated in a velvet-like film (“Velvet Disease”). Another protozoan that can commonly cause white spots on freshwater aquarium fish is the ciliate Icthyophthirius multifiliis, or “ich.” White spots caused by Ichthyophthirius, however, differ from those caused by Oodiniumin in that they are described to look like white grains of salt or sugar on the bodies, fins, and gills of fish. Also, Icthyophthirius sp. has a characteristic horseshoe-shaped macronucleus.
A female domestic shorthair cat recently adopted from the shelter was brought to her new veterinarian for a routine check-up. Fecal flotation revealed the egg below (shown in two different planes of focus). What parasite is this?
Aonchotheca putorii eggs have characteristically deep striations on their shell surface. The adult worms are found in the stomach and small intestine of mustelids, raccoons, bobcats, and other mammals. Infection of domestic cats appears to be confined to the stomach and may cause gastritis.
A 7-yr-old intact female llama presents for being unable to rise for 4 hours. She has a 2-week history of diarrhea and inappetence. She has a body condition score of 2/5, pale mucous membranes, and bloodwork reveals regenerative anemia, hypoalbuminemia, hypoproteinemia, hypokalemia, and hyponatremia. A fecal recovers the organism shown below. What is the llama infected with?
he llama is infected with Eimeria macusaniensis. The oocysts of this coccidial species are characteristically large, dark, and have a horseshoe shape. Clinical signs associated with E. macusaniensis infection are most often seen in juvenile camelids; however, older camelids without a history of appropriate parasite control may present with severe clinical abnormalities including anemia, diarrhea, and lethargy progressing to inability to rise. Animals with this presentation have a guarded prognosis without appropriate supportive care.
A client brings in a 6-year-old spayed pug-mixed dog and complains that the dog is shedding numerous “worms” from its anus. You examine the dog’s perianal area and obtain a white, rice-like “worm” and tease it open with forceps. You examine its contents on a microscope slide. What parasite is this?
These are Dipylidium caninum eggs. The “worms” the client described were actually tapeworm segments (proglottids). This is a very typical presentation for tapeworm infection. Animals acquire Dipylidium caninum through the ingestion of infected fleas containing cysticercoids
Two 6-month-old, male, red angus with a 6-week history of lethargy, weight loss, and progressive weakness were found down, and died a week later. Previous blood work was negative for Anaplasma and leukemia. Fecal flotations were positive for Trichostrongyle eggs, with egg per gram counts of 8,650 and 10,550. Microscopic examination of the anterior end an adult:
These are Haemonchus sp adults. Haemonchus spp., commonly known as the barber’s pole worm, feed on blood in the abomasum. In fresh necropsy samples, the blood-filled gut of female worms can be seen intertwined with the ovaries, giving them a barber’s pole or candy cane appearance. The blood-feeding from the adult Haemonchus can lead to anemia and loss of productivity, and in animals with large numbers of adults feeding in the abomasum, death.
A 2-yr-old 240 kg female horse pastured with a herd in Okmulgee, Oklahoma was euthanized after being found down and unable to rise in mid-April. Necropsy revealed a marked reduction of skeletal muscle, prominent gelatinous edema along the ventral midline, and pale musculature and mucous membranes. Cyathostome larvae were observed embedded in the mucosa of the large colon and cecum. Three types of nematodes were found in the small and large intestines. The stalk of the cranial mesenteric artery was obstructed by a thrombus containing an approximately 0.5 cm nematode larva. Several cyathostome adults and the following 3 nematodes were submitted to a diagnostic lab for identification.
Nematodes from euthanized horse submitted for identification:
This horse likely died of severe parasitism by both large and small strongyles. The thrombus in the mesenteric artery is a hallmark finding of Strongylus vulgaris infection. However, the nematodes submitted to the diagnostic lab for identification lacked the characteristic “teeth” of S. vulgaris within the buccal cavities. Based on morphological characteristics, the submitted strongyles are likely Strongylus edentatus.
Below are photos taken during surgery of a mass in a dog from Saskatchewan.
This is a PCR confirmed case of hepatic alveolar hydatid disease caused by Echinococcus multilocularis. This is unusual because dogs are generally the definitive, not intermediate, host for this tapeworm. This represents approximately the 5th case of alveolar hydatid disease diagnosed in dogs in Canada in the last 5 years, and suggests that this parasite is emerging as a threat to the animal, and possibly human, health in North America.
A rescue dog from Walpole Island near London, Ontario was euthanitized due to heart failure subsequent to heart worm infection. The dog was posted to collect the heart and Dirofilaria immitis. Incidentally, these worms were also collected - three from the right kidney, which was obliterated, and four that were free in the abdomen. What are these?
These are Dicotophyme renale, commonly (and appropriately) called the giant kidney worm. This nematode parasitizes the kidneys (usually the right) and occasionally the peritoneal cavity of dogs, mink, and other domestic and wild animals, and requires an annelid primary intermediate host and a fish secondary intermediate host. Although infection does eventually lead to kidney destruction, animals are most often asymptomatic. The giant kidney worm is found worldwide, but cases are relatively rare in North America.
A greyhound in Oklahoma that is used to hunt coyotes is presented with lethargy and fever. A CBC reveals anemia. The owner provides proof of current vaccinations and states that routine flea/tick prevention is used. The referring veterinarian suspected Rocky Mountain Spotted Fever but the dog did not improve with doxycline. A photograph of the greyhound is included below. Note the suspicious fighting lesions on the face.
The arrows are pointing to two small piroplasms. Most commonly Babesia gibsoni is the small piroplasm of dogs that is associated with direct transmission through fighting (particularly among fighting pitbull circles) in Oklahoma. However genetic characterization identified the parasite as Babesia conradae, a small piroplasm, morphologically indistinguishable from B. gibsoni, most commonly reported in dogs from California (and at the time of this case, had not been documented in dogs outside of California). Interestingly, the owner was quite adamant that this greyhound had never been to California; The owner had purchased the dog as a young puppy from a breeder in Kansas, and the dog had since never been out of Oklahoma.
Microscopic examination of debris from quills of a zoo hedgehog with crusts around the face and quill loss revealed the following ectoparasite
This is Caparina tripilis, a mite of hedgehogs that can cause pruritus, erythema, quill loss, and crusts along the face. Severe infection may lead to death. These mites can be differentiated from other mites by being visible to the naked eye as small white specks and having 3 long hairs on the third and fourth pairs of legs.
A fecal flotation was performed on a fecal sample collected from a miniature heifer. In addition to strongyle eggs, which other parasite egg is present (indicated with arrows)?
These eggs are Strongyloides eggs. Strongyloides eggs are shed in the feces, releasing the first-stage larvae. After a period of free-living development in the environment, they develop into the infective third-stage larvae. Modes of transmission include ingestion of the third-stage larvae, penetration of the skin, and transmammary. Strongyloides eggs may be confused with stongylid eggs, which are more common to see in horse fecal flotations. However, the two types of eggs are easily distinguished because Strongyloides eggs are smaller and contain larvae when passed in feces.
Magnified view of the cuticle of a parasite coughed up by a dog.
This is a pentastomid (likely Linguatula serrata), a parasitic arthropod. Cuticular spines can be seen on each pseudosegment. The adults most commonly infect nasal passages of predacious mammals, reptiles, and birds. Intermediate hosts include small herbivores and fish, which become infected by ingesting eggs expelled from the respiratory tract or the feces of the definitive host. The larvae encyst in the viscera of the intermediate host and develop into nymphs. These parasites are also a zoonotic risk, as the human can serve as an accidental intermediate host, and rarely a definitive host.
A teacup pig named “Ham Newton” was presented with alopecia, abscesses, and hyperkeratosis in the facial region, comedones near the mouth, ear pinnae and nose, pruritis, and weight loss.
This parasite is Demodex phylloides, which is part of the normal cutaneous fauna of pigs. As with dogs and cats, demodectic mange in pigs is only seen in immunocompromised animals or those with severe nutritional deficits.
A veterinarian doing the first pregnancy check of the season on a small beef ranch (20 cows/heifers, 1 bull) finds a high number of open cows. One cow is noted to have a small amount of mucopurulent vaginal discharge. Also, the rancher mentions that he found an aborted calf last week. The rancher recently purchased a new bull, and a breeding soundness exam was performed on the bull prior to purchase, and he has observed the bull mating, but due to the number of open cows, he would like further testing to confirm the bull is fertile. A preputial wash and culture is performed, and after 48 hours, a sample is spotted onto a slide and fixed/stained. The parasite below is observed under the microscope:
These are trophozoites of Tritrichomonas foetus, which is a sexually transmitted parasite that causes early embryonic death and abortions between 2-4 months of gestation. The main clinical signs in cows include infertility, pyometra, abortion, vaginitis, cervicitis, endometritis, and salpingitis. Bulls most commonly display no clinical signs. There is no approved FDA treatment for infection with this parasite. Recommendations are to test bulls for infection prior to introduction onto a farm, cull those identified as infected, and allow infected cows to have at least four months of breed rest to clear the infection.
A domestic short-haired cat in poor body condition was taken to an animal shelter. This parasite was combed from the cat’s hair.
This is Felicola subsotratus, a chewing louse of cats. Note that the head is nearly as wide as the thorax, which allows this louse to feed on tissue debris. The wider head is characteristic of chewing lice, in contrast to sucking lice, which have a narrower head to facilitate blood-feeding. This louse also has characteristically angular mandibles. Typically only older cats that do not groom themselves thoroughly or distressed cats become infested with lice.
An owner in Alva, Oklahoma lost 5 to 6 calves that were 4-6 weeks of age to an unknown illness. The calves were treated with several different antibiotics prior to death. Necropsy revealed mild inflammation of the small intestine, small 1/2 cm diameter hemorrhages in the cecum, and loose green stool throughout the intestinal tract. A fecal flotation was performed on a cecal wall scraping and the following organism was observed.
These are oocysts of Eimeria zuernii, a causative parasite of winter coccidiosis. The onset of clinical signs corresponds with parasite gametogony within the intestinal tract and the associated destruction of mucosal cells. Tenesmus and bloody diarrhea are typical clinical findings. The pathologist remarked that the level of infection and tissue destruction was the worst that he had seen in a coccidiosis case
A middle-aged spayed Cocker spaniel was referred to a veterinary specialty clinic due to suspected allergies because of a history of papular rashes and pruritis on its front and rear limbs. A skin scraping of a scaling papular area on the top of the head was performed, and this parasite was observed under the microscope
This is Cheyletiella yasguri. Cheyletiella spp. are easily identifiable because of morphological features including pronounced palpal claws. When infested with these mites, dogs develop dermatitis with branlike exfoliative debris that stirs from the movement of the actual mites, a condition termed “walking dandruff.” These mites are large enough to be seen with the unaided eye. This mite is relatively uncommon and occurs most often on puppies in breeding facilities
A Tampa, Florida family recently adopted a young adult female domestic cat from a local shelter. The animal was active and healthy, but its hair coat was dull and breakable. The cat was presented to a local clinic for vaccination, and the veterinarian observed some small ectoparasites throughout the cat’s hair coat, conferring a ‘salt and pepper’ appearance. Plucking some hairs at the base of the tail and examining them under a stereomicroscope revealed the ectoparasites below:
Salt and pepper appearance of the cat’s hair coat:
This is the cat fur mite Lynxacarus radovskyi (Listrophoridae), which has a wide geographic distribution including warm regions of North America (with reports in Florida, Texas, and Hawaii), South America (Brazil), the Caribbean (Puerto Rico), and also countries in southeastern Asia (Malaysia, Philippines) and Oceania (Australia, New Zealand, and Fiji). The species is easily differentiated from other mites (Cheyletiella blakei, Demodex gatoi, and D. cati) and lice (Felicola subrostratus) that infest cats by its body shape and color. Unlike many mites and lice, the body is cylindrical and dorsally arched, with a strongly chitinized anterior part (head or propodosome) which is light brown in color, and the rest of the body (idiosoma) being poorly chitinized and light-colored. The color contrast of these two parts of the mite’s body with the light or dark hair coat of the host is responsible for the commonly noticed “salt and pepper” aspect. Adult males and females measure around 0.5 cm. Infestation is commonly subclinical, but dull and broken hair coat is often observed. However, there have been reports of pruritus and papular dermatitis in infested cats (other ectoparasitic infestations or allergy may be the main cause of these clinical signs).
Identify this arthropod from the ear of a dairy goat.
The long, segmented pedicels are typical of Psoroptes spp. Psoroptes cuniculi has been isolated from the ears of domestic rabbits, goats, and horses. Clinical signs in goats include ear scratching, head shaking, and occasionally alopecia or crusty lesions. Psoroptes cuniculi is often limited to the ears in goats but can spread to the head and body. It has been proposed based on phylogenetic analysis that P. cuniculi and Psoroptes ovis(the causative agent of sheep scab) are a single species. This could have important implications as P. ovis is a reportable disease both federally and in many states.
A woman was making breakfast with organic eggs from free-range chickens that she purchased from a major department store chain. Below is what she found after cracking the second egg.
This is Ascaridia galli, a parasitic roundworm of birds. This nematode inhabits the small intestines, but in heavy infections, may move up the oviduct and can sometimes be found in hens’ eggs. The life cycle of this parasite involves the ingestion of infective eggs, but transport hosts such as earthworms are thought to play a role in A. galli transmission, and therefore free-range birds tend to have a higher risk of infection.
A 9-year-old Arabian gelding was presented for a large ulcerated mass on the dorsal aspect of the pastern of the right forelimb. Radiographs showed no deep tissue involvement. Surgical removal was elected.
This is a case of cutaneous habronemiasis, or “summer sores”. This condition may result from the entry ofHabronema 3rd-stage larvae into an open wound (or mucous membrane) when several fly species feed. Larvae do not mature, but instead, die in situ. The larvae deposited in wounds or at mucocutaneous junctions can cause proliferative lesions that grow and ulcerate throughout the fly season.
A roadkill raccoon from central Texas was submitted for necropsy. These parasites were detected in the pancreatic duct:
This parasite is Eurytrema procyonis, which lives in the pancreatic ducts of raccoons. In the stained histologic images above, small, thick-walled oval eggs can be seen within the bodies of the adult flukes. The first intermediate host of this parasite are land gastropods. The second intermediate host has not been determined but is hypothesized to be an arthropod that ingests cercariae in extruded sporocysts from snails.
A 9-week old Beagle puppy from Oklahoma near the Texas border was presented with syncope, labored breathing, and ascites. Electrocardiogram revealed prominent conduction abnormalities. The pup was euthanized due to cardiac decompensation. A Giemsa stained blood smear was prepared prior to euthanasia. The organisms below were observed by microscopy (100X objective)
These are trypomastigotes of Trypanosoma cruzi, causative agent of Chagas Disease, or American Canine Trypanosomiasis. Trypanosoma cruzi is endemic in parts of Texas, and is transmitted by triatomine bugs (commonly called “kissing” or “assassin bugs”) via the stercorarian route. Metacyclic trypomastigotes deposited by infected triatomines invade cells near the bite site or of intact mucosa and rapidly transform into amastigotes, which undergo repeated rounds of asexual reproduction. Trans-placental transmission of the parasite is also documented. Trypanosoma cruzi disseminates in the vertebrate host, and damage is particularly pronounced in cardiac tissue in acute and chronic canine Chagas infections.
A Louisiana producer contacts you regarding high mortality rates in his channel catfish (Ictalurus punctatus) from multiple ponds on his property. The majority of fish affected are smaller in size and are commonly seen swimming listlessly near the water’s surface. He sends you multiple specimens, along with water and benthic sediment samples. Histologically, you note granulomatous branchitis, with cartilage necrosis, inflammation, and hyperplasia. Also, myxozoan parasites are present and are surrounded by inflammatory cells.
The catfish are being parasitized by Henneguya ictaluri, which causes the pathognomonic proliferative gill disease (PGD) commonly called “Hamburger Gill”. The proposed lifecycle involves channel and blue catfish and the common oligochaete Dero digitata. Actinospores are released into the aquatic environment by D. digitata. Fish come into contact with the actinospores orally or through the skin or gills. Development to the final myxospore stage in fish occurs in the gills. Upon release into the environment, the myxospores infect D. digitata oligochaetes. The myxozoan has been associated with commercial fish die-offs in the southeastern United States, typically during the Spring and Fall.
Fifteen fecal samples from cows in Muskogee, OK were submitted to the Oklahoma Animal Disease Diagnostic Laboratory in Stillwater, OK as part of a routine wellness screen. The veterinarian that submitted the samples was specifically curious about Fasciola hepatica infections. Fecal sedimentations were prepared, and the following egg was detected from one of the cows
This is not an egg of Fasciola hepatica, but rather an egg of Paramphistomum cervi, commonly known as the rumen fluke. Although F. hepatica and P. cervi have similar life cycles, requiring an aquatic snail as an intermediate host and encysting as infective metacercariae on aquatic vegetation, they inhabit different locations within ruminant hosts as adults; Fasciola hepatica resides in liver bile ducts, while P. cervi parasitizes the rumen, as its common name implies. The eggs of these two flukes also appear similar. Both are large (~120 µm length) and ovoid with an operculum. Eggs of F. hepatica, however, are yellow-brownish while P. cervin eggs are relatively clear. Staining with methylene blue may help to distinguish the coloration better, as stained F. hepatica eggs will appear amber in color while P. cervi eggs will still appear relatively clear.
These skin lesions were identified on the ear of an opossum. What parasite is most likely responsible for the dermal cysts seen?
These are macroscopic cysts of Besnoitia. Besnoitia darlingi is common in the Virginia opossum and causes large skin cysts containing bradyzoites. Cysts are most commonly identified in the ears of opossums collected in the summer months. Infection is often well-tolerated, but clinical disease, including anemia and renal damage, is commonly reported, particularly in debilitated opossums
Image: Besnoitia bennetti. A small portion of the material from an opened cyst from the same donkey showing the massive number of bradyzoites that are within each of these cysts that appear in and on these animals. (Fig 3.47; Georgi’s 11ed)
A great blue heron was brought into the Oklahoma State University Center for Veterinary Sciences Avian, Exotics and Zoo Medicine Department because it appeared extremely emaciated. While performing a general physical examination, the veterinarian discovered these organisms in the oral cavity.
The organism was identified as Clinostomum marginatum based on host, where the adult worms were located, and morphology. This trematode, commonly called the “yellow grub”, is found in many freshwater fish in North America, which serve as the second intermediate host (the first intermediate host is the Helisoma sp. snail). Many aquatic bird species including herons can become infected by ingesting infected freshwater fish. Yellow grub adults parasitize the mouths and throats of birds. Fluke eggs are swallowed and passed in the feces of infected birds.
Ohli is a 4-year-old female spayed Pomeranian mixed breed dog. Ohli was traveling with his owners from Virginia to northern Michigan in April 2016. The dog presented to a veterinary clinic in Michigan with paralysis of all four limbs coupled with dyspnea and dysphagia. Upon thorough examination, four ectoparasites were found attached to the right pinna and dorsal neck area. What is causing the paralysis and what are these ectoparasites?
Tick paralysis caused by infestation with Dermacentor variabilis. Tick paralysis is a neurologic toxicosis resulting from unidentified toxins in tick saliva. In the United States, infestations with Dermacentor spp. are most often implicated for causing tick paralysis in animals and humans. However, bites from other tick species including Ixodes, Amblyomma, and Rhipicephalus may result in paralysis of a variety of animals throughout the world. Prompt removal of all attached ticks alleviates the paralysis almost as quickly as the neurologic condition set in. The application of an approved acaracide helps prevent and control future infestations.
Beelzebub is a 6-month-old Hereford show calf that presented for lethargy to a clinic in Louisiana. Blood culture resulted in significant numbers of motile parasites. Blood film evaluation (below) revealed several protozoan parasites. What is the parasite?
Trypanosoma theileri; a non-pathogenic hemoflagellate parasite of cattle throughout the world. Transmission of T. theileri to cattle is through the feces of infected horse flies (i.e., stercorarian transmission). Pathogenicity of T. theileri has never been demonstrated conclusively and infection is considered subclinical. Trypomastigotes of T. theileri are considered an incidental finding and other causes of the clinical signs observed should be considered. However, when present as a co-infection with other pathogens (e.g. Anaplasma marginale), some believe that T. theileri may be pathogenic or contribute to the clinical disease process.
Thirteen Dachshund puppies ranging in age from approximately 6 to12 weeks were rescued from an unlicensed breeding facility in Virginia. The puppies, as well as the dogs used for breeding, had been housed outdoors in metal crates. All of the dogs were emaciated, infested with fleas and ticks, and heavily coated in mud and feces. The dogs were confiscated and taken to a nearby animal hospital, where they were physically examined to assess their overall health. As part of the exam, direct fecal smears and fecal flotations were performed. The following organism (~300 um in length) was found in fecal smears from several of the dogs:
The size and distinct esophageal bulb allow identification of this organism as a rhabditiform Strongyloides sp. larva. The Baermann technique is a sensitive method to recover this parasite stage in feces, but larvae are also often found on direct smear.
Strongyloides stercoralis can infect both dogs and humans. Infection is often associated with poor sanitation and crowding. Parasitic worms are female and reside embedded in the mucosa of the small intestine. Mature females reproduce by parthenogenesis and release eggs which often hatch within the intestine and rhabditiform larvae are passed in the feces of the definitive host. In the environment, the rhabditiform larvae undergo successive molts to become either filariform larvae or free-living adult males and females. Filariform larvae are infective to definitive hosts by ingestion or skin penetration, which may give rise to dermatitis. Larvae then enter the circulation and lymphatics and migrate to the small intestine via several pathways to become adult females.
Strongyloides stercoralis infections are notoriously chronic due to autoinfection, which occurs when rhabditiform larvae develop to filariform larvae within the large intestine and penetrate the intestinal mucosa or perianal skin. Immunosuppression may allow the parasite to disseminate to other organs. Disseminated strongyloidiasis is often amplified by autoinfection, and is a life-threatening condition. (The photomicrograph used to illustrate this case was acquired from the Centers for Disease Control website.)
Sheep in a small flock on a southwest Texas farm is noted to be losing patches of wool. Some of the sheep have been observed to scratch themselves against trees and fence posts, and pieces of wool are regularly being left behind. Tags of wool on the animals appear to be sloughing off. A few of the animals have areas of severely excoriated skin due to intense scratching. A sample of wool and serous crusting are submitted to a parasitology diagnostic lab. This organism was found in the crusted serous material (100X total magnification).
The organism above causing the pruritic condition in the sheep is Psoroptes ovis. Note the acarine’s long legs, and the pretarsi with long-three-segmented pedicels. This mite does not burrow into the skin. Instead, it remains at the base of the hair and uses its stylet-like chelicerae to pierce the skin, resulting in serum exudate which will scab. This form of mange is commonly called scabies or “scab”. When skin areas become overly hardened with crusted serous material and debris from scratching, the mites migrate to new areas, resulting in hair loss and scabbing that spread over the surface of the body. In addition to economic loss due to compromised wool production and quality, psoroptic scab can be devastating to the health of sheep, as they may become severely debilitated, and perhaps even die. The condition is reportable.
A one year-old intact male husky was presented to the Oklahoma State University Center for Veterinary Health Sciences (OSU-CVHS) Emergency facility for seizures that had begun 2 days prior. According to the referring veterinarian, the patient had a history of heavy ectoparasite infestation and was positive for hookworm infection by fecal flotation. The husky tested negative to all analytes on the IDEXX 4DX Snap Plus ELISA. The dog was admitted to the Intensive Care Unit (ICU), where neurologic signs progressively worsened, with left-sided padding of front and hind limbs, ataxia, conscious proprioception deficits on all limbs, but deep pain intact noted. Ultimately, the animal coded in the ICU and was humanely euthanized. Grossly, necropsy revealed severe, acute multifocal, locally extensive cerebral hemorrhage with flattening of gyri and cerebellar coning. A sample was taken for histopathology. Microscopic evaluation of brain tissue revealed acute, severe, multifocal, hemorrhagic and necrotizing, neutrophilic meningoencephalitis with intralesional organisms that were 10-20 microns and circular. See below (left). A sample of brain tissue was submitted to the Centers for Disease Control. See the resulting indirect immunofluorescence stain of brain tissue below (right).
The indirect immunofluorescence assay performed by the CDC confirmed the presence of Balamuthia mandrillaris, a free-living amoeba naturally found in the environment. This parasite can cause a rare and serious condition of the brain and spinal cord termed Granulomatous Amebic Encephalitis (GAE) in humans and dogs. Balamuthia lives freely in soil, and also may be present in freshwater. Cysts and trophozoites (the infective form) of the parasite may enter the vertebrate host in various ways, including through nasal passages to the lower respiratory tract or through ulcerated or broken skin.
An adult female red-tailed hawk was found on highway 177 in Oklahoma in early November. It was presumed that the bird was hit by a car. The hawk was placed on IV fluids and force fed. CBC revealed immature Leucocytozoon stages. Metronidazole, meloxicam, and baytril were administered, but no response to treatment led to euthanasia. Other parasitological findings are listed below. Can you identify the types of parasites recovered from the red-tailed hawk based on the respective morphological characteristics of each?
- Parasite A = trematode eggs
- Parasite C = trematode adults (3 different species were identified)
- Parasite B = ascarid egg
- Parasite D = ascarid adult (species not identified)
The eggs of Parasite A are operculated, and the adults of Parasite D appear to have oral suckers, indicating these parasites are likely trematodes. The egg of Parasite B is round with a characteristic thick “bumpy” or pitted shell and ~80 um in diameter, and the adult of Parasite D is large (~7 cm) and has 3 lips on anterior end (posterior end does not taper to a fine point), indicating both egg and adult belong to family Ascarididae.
A small herd of Woodland caribou resides in a wildlife sanctuary in central Oklahoma (in the town of Washington ~1.5 hours from Oklahoma State University). Over the summer, one of the animals, nicknamed “Rudolph”, is noted to have a head tilt, is wandering away from the rest of the herd, and appears to be circling to the right. Rudolph’s condition rapidly worsens, and he is humanely euthanatized. Necropsy reveals the presence of many trichostrongyles in the stomach and small intestine and the following organism in the cranial meninges. Fecal analysis shows a large number of trichostrongyle eggs.
This is likely Parelaphostrongylus tenuis, or brainworm. Terrestrial snails serve as the intermediate host of this parasitic nematode, and upon accidental ingestion of snails through grazing, a variety of ruminant hosts can become infected. The natural definitive host of P. tenuis is the white-tailed deer, which shed larvae in feces infective to snails. Other ruminants are considered aberrant hosts, as infections are rarely patent (no larvae observable in feces) and neurologic illness develops in response to migrating and developing worms.
