Bursate

Ancylostomatoidea - Hookworms

Ancylostoma braziliense
Buccal cavity of adult Ancylostoma braziliense. Note the single pair of cutting teeth.

Ancylostoma caninum
Egg of Ancylostoma caninum in a fecal flotation from a dog. Eggs have an elliptical shape, thin shell, and are approximately 52-79 X 28-58 µm. In fresh feces eggs contain morulae, which develop to first stage larvae within eggs in the environment.

Ancylostoma caninum
Buccal cavity of adult Ancylostoma caninum. Note the three pairs of cutting teeth. Pathogenesis of infection with Ancylostoma caninum is associated with feeding habits of the adult parasite, which leads to blood loss of an estimated 0.01 to 0.09 ml/worm/day.

Ancylostoma caninum
Male and female Ancylostoma caninum recovered from a dog. Adults males are usually 10-12 mm in length, and the females average 14-16 mm in length. Prepatent period varies by route of transmission and can be as short as 2 weeks when larvae are ingested or as long as 4 weeks when larvae are acquired by dermal penetration.

Ancylostoma caninum ​
​In situ photo of Ancylostoma caninum found on necropsy of a dog. Infected dogs may present with anemia from blood loss due to worm feeding, skin lesions associated with penetration of third-stage larvae, diarrhea associated with fourth-stage larvae damaging the small intestine, and/or hemorrhagic pneumonitis associated with larval migration.

Ancylostoma caninum
Adult of Ancylostoma caninum in small intestine from dog at necropsy. Note the area of hemorrhage surrounding the adult.

Ancylostoma tubaeforme
The buccal cavity of the hookworm of cats. Although very similar to the stoma of adult Ancylostoma caninum, the teeth on the ventral margin of Ancylostoma tubaeforme are slightly larger. Infection with this species is the result of skin penetration or ingestion of third-stage larvae, or ingestion of paratenic hosts with larvae encysted in tissues.

Bunostomum sp.
Species of Bunostomum most commonly infect ruminants. A large buccal cavity with cutting plates helps differentiate these hookworms from other intestinal parasites.

​Bunostomum phlebotomum
A parasite of cattle and zebu, Bunostomum phlebotomum may be found in the small intestine feeding on blood. Penetration of larvae may cause cattle to stamp their feet and lick their legs, and heavy infections with adults may lead to diarrhea, anemia, and hypoproteinemia. In calves this manifests as marked weakness, emaciation, and submandibular edema.

Uncinaria stenocephala
Egg of Uncinaria stenocephala. This hookworm infects dogs (rarely cats) in cooler temperate regions, including the northern US, Canada, and Europe. Eggs resemble those of Ancylostoma spp. in that they are elliptical, thin-shelled, and contain morulae in fresh feces, but Uncinaria eggs are slightly larger (71-92 X 35-58 µm).

Uncinaria stenocephala and Ancylostoma caninum
Eggs of Uncinaria stenocephala and Ancylostoma caninum together in a 10X field of view. Note the size difference between eggs of the two species. Photomicrograph provided by Dr. Michael Dryden, Kansas State University.

Uncinaria stenocephala and Ancylostoma caninum
Egg of Ancylostoma caninum on the left and Uncinaria stenocephala on the right in 40X field of view. Photomicrograph provided by Dr. Michael Dryden, Kansas State University.

Uncinaria stenocephala
Buccal cavity of Uncinaria stenocephala. Note the two cutting plates.

Dioctophymoidea

Dioctophyme renale
Eggs of the giant kidney worm, Dioctophyme renale, are passed in the urine of infected hosts. Eggs have a thick, rough shell and measure 60–80 µm by 39–46 µm.

Dioctophyme renale
Adult Dioctophyme renale in the kidney of a dog. Primarily a parasite of mink, other animals, including domestic dogs, other canids, and occasionally pigs, horses, cattle and humans may be infected.

Dioctophyme renale
Adult Dioctophyme renale removed from a coyote. This parasite can also infect humans. Adult female worms may reach 103 cm in length, making Dioctophyme renale the largest nematode known to parasitize humans.

Metastrongyloidea

Aelurostrongylus abstrusus
First-stage larva of Aelurostrongylus abstrusus can be recovered from the feces of infected cats using a Baermann apparatus or zinc sulfate flotation. Larvae are approximately 300–400 µm by 15–20 µm with a terminal S-shaped kink and dorsal spine.

Crenosoma vulpis
Anterior end of Crenosoma vulpis showing the overlapping circular folds unique to the family Crenosomatidae. Adults of this genus are found in the bronchi and trachea of animals. Cresonema vulpis is a cause of substantial chronic tracheobronchitis in captive fox.

Filaroides osleri
Nodules of Filaroides osleri in dog lung. First-stage larvae of Filaroides spp. may be recovered from feces or transtracheal washes. Larvae recovered from feces are 232–266 µm in length whereas larvae from transtracheal washes measure 325–378 µm.

Metastrongylus sp.
Metastrongylus sp. in the bronchus of a pig. Female Metastronglus spp. produce eggs that when passed in feces are larvated and can be detected with flotation.

Metastrongylus apri
Ventral view of the bursa of a male Metastrongylus apri. Adult males may reach 25 mm in length and females may reach 58 mm in length.

Muellerius sp.
First-stage larva of Muellerius sp. recovered from sheep feces. Larvae have an S-shaped kink on posterior end, cuticular spine, and measure 300–320 µm in length.

Muellerius capillaris
Goat lungs showing classic Muellerius capillaris lesions. Adult worms of this genera live in the alveoli and pulmonary parenchyma of sheep and goats. There, they form nodules that turn a greyish color, a result of the degeneration of accumulated leucocytes and necrotic pulmonary tissue. Despite this, hosts generally show no apparent clinical signs.

Parelaphostrongylus tenuis
First-stage larva of Parelaphostrongylus tenuis from a white-tailed deer. Larvae are readily recovered using a Baermann apparatus and measure 310–380 µm in length. Larvae have an S-shaped kink in the tail and a dorsal spine.

Parelaphostrongylus tenuis
Adult Parelaphostrongylus tenuis adults in the subdural space of a white-tailed deer. Adults are 39-91 mm in length.

Parelaphostrongylus tenuis
Neurologic signs of a goat infected with Parelaphostrongylus tenuis. When Parelaphostrongylus tenuis infects a host other than the white-tailed deer, the larvae migrate aberrantly, usually causing damage to the dorsal horns of the grey matter of the spinal cord. Small ruminants are particularly susceptible to neurologic disease due to aberrant migration of Parelaphostrongylus tenuis.

Protostrongylus rufescens
Nodules of Protostrongylus rufescens in sheep lung. Adult Protostrongylus rufescens live in the small bronchioles and may induce nodule formation.

Stephanurus dentatus

Adult Stephanurus dentatus removed from the kidney of a pig. Known as the kidney worm of swine, adults are found in the perirenal fat, the renal pelvis, and the walls of the ureters. Adult males are 20-30 mm and females are 30-45 mm in length.

Adult Stephanurus dentatus excised from cysts in the perirenal fat surrounding the ureter of a pig. Adults are usually found in cysts that communicate with the ureter through which they pass their eggs. The eggs leave the host via urine. Host infections may be acquired through ingestion of third-stage larvae, ingestion of a paratenic host, or from dermal penetration by the third-stage larvae. The larvae then migrate extensively through the organs.

Strongyloidea - Large and Small Strongyles

Strongyle-type egg
Eggs of Strongyloidea have this typical morphology. They are elliptical, have a thin shell, and are approximately 65-100 X 34-50 µm, depending on the species. In fresh feces eggs contain morulae which develop into first stage larvae within eggs in the environment.

Strongyle-type egg
A larvated strongyle egg is shown. Larvated eggs are often seen in fecal samples that have been stored for several days before processing.

Small strongyles
Several different species of adult small strongyles (cyathostomins) from the large intestine of a horse. Over 50 species of equine small strongyles have been described.

Small strongyle
​Buccal cavity of a small strongyle adult. Buccal cavities of small strongyles are smaller than those of large strongyles. Also, note the outer leaf crown on this specimen.

Strongylus spp.
Adult large strongyles (Strongylus spp.) from the large intestine of a horse. The three main species of Strongylus are Strongylus vulgaris, S. equinus, and S. edentatus .

Strongylus edentatus
Strongylus edentatus is differentiated from other members of the genus by a buccal capsule that it is wider anteriorly than at the middle and, as suggested by the species name, a lack of teeth.

Strongylus equinus
The buccal capsule of Strongylus equinus. Strongylus equinus makes an extensive migration through the abdominal cavity, taking 260 days to molt and mature to a patent adult.

Strongylus vulgaris
Buccal cavity of Strongylus vulgaris. Note the two prominent cutting teeth and outer leaf crown.

Strongylus vulgaris
Colic in horses may result from migration of juvenile Strongylus vulgaris through the cranial mesenteric artery.

Gross lesion due to horse strongyles
Thrombosis in the illiac artery of a horse, a result of migrating juvenile strongyles.

Trichonematidae

Chabertia ovina
Large buccal cavity of an adult Chabertia ovina. This parasite is found in the colon of sheep, goats, and cattle throughout the world and feeds on the granular layer that it digests with esophageal secretions. Blood feeding is incidental and may be a cause for frank blood in the feces of the host.

Oesophagostomum radiatum
The nodular worm of cattle, zebu, and water buffalo takes its common name from the characteristic nodules formed around larvae in the intestine of an infected host.

Oesophagostomum columbianum
​Nodules formed by Oesophagostomum columbianum in the colon of a sheep. Oesophagostomum columbianum is a parasite of the colon of sheep, goats, camels, and wild antelope. Their larvae encyst anywhere from the pylorus to the colon to complete their development and become adults that attach in the colon. Frequently, the larval nodules become abcesses that are filled with caseous material.

Trichostrongyloidea

Trichostrongyle-type egg
With the exception of Nematodirus spp., eggs of Trichostrongyloidea species have this typical morphology. They are elliptical, have a thin shell, and are approximately 65-100 X 35-50 µm, depending on the species. In fresh feces eggs contain morulae which develop to first stage larvae within eggs in the environment.

Cooperia spp.
Transverse striations along the cuticle of a Cooperia sp. adult cleared in lactophenol.

​Dictyocaulus spp.
Dictyocaulus viviparus first-stage larva (arrow) recovered from bovine feces. These larvae are approximately 300-360 µm in length and are best recovered using a Baermann apparatus on fresh feces.

Dictyocaulus viviparus
Adult Dictyocaulus viviparus seen in the bronchi of a steer. Dictyocaulus viviparus parasitizes cattle, deer, reindeer, buffalo, and camels. Adults may reach 4-8 cm in length.

Haemonchus spp.
Species of Haemonchus are referred to as barber-pole worms. Their common name reflects the distinct appearance of the female worms - a white uterus wrapped in a spiral fashion around the blood-filled intestines, which appear red in fresh worms.

Haemonchus contortus
Haemonchus contortus are shown feeding in the abomasum of a sheep. When the adults and fourth stage larvae move and leave their initial feeding sites, the wounds continue to bleed into the lumen of the abomasum.

Haemonchus contortus
Third-stage larvae of Haemonchus contortus suspended in a dew drop on grass. Hosts acquire infections with this parasite when they directly ingest larvae from pasture.

Haemonchus contortus
Submitted by Erin Edwards, Texas A&M Veterinary Medical Diagnostic Lab (TVMDL).
2nd Place – Nymphal Place 2020 NCVP Photo Contest.

Haemonchus contortus
Infection with Haemonchus may overwhelm a host's ability to replace proteins and blood lost. This results in decreased intravascular oncotic pressure resulting in edema. The gathering of edema in the submandibular area is termed 'bottle jaw'.

Nematodirus spp.
Egg of Nematodirus sp. Eggs are elliptical, approximately 152-260 X 67-120 µm in size depending on the species, and contain two to eight distinctive large cells in fresh feces. ​

Nematodirus sp.
Spicules and bursa of a male Nematodirus sp. Clinical signs of infection are associated with the emergence of larvae from the mucosa. This manifests as inappetence and acute enteritis.

Ollulanus tricuspis
Larva of Ollulanus tricuspis. Third-stage larvae are approximately 500 µm and have a tricuspid tail similar to that of the adult female (2nd and 4th stage larvae also have this type tail). Adults and larvae are found in the stomach of domestic cats and other felids. Diagnosis is based on the identification of larvae or small adults (1 mm) in vomitus using the Baermann test.

Ollulanus tricuspis
A gravid Ollulanus tricuspis female. In this species, the larvae develop in the uterus of the female until they reach the third stage. Infection is spread when the larvae are vomited and another cat ingests them.

Ostertagia sp.
Anterior end of Ostertagia sp. showing the short buccal cavity and cervical papillae used to differentiate this worm from other trichostrongylids.

Ostertagia ostertagi
Abomasum from a calf infected with Ostertagia ostertagi. The mucosal surface of the abomasum is covered with pin-head to pea-sized nodules as a result of invasion of juvenile worms into gastric glands.

​Trichostrongylus spp.
Adult Trichostrongylus species have a distinct excretory notch visible in the esophageal region.

Trichostrongylus spp.
Species of Trichostrongylus are differentiated from other nematodes by the short and pointed spicules of males.