Parasitology

Last updated on April 30, 2002

Descriptions of parasites by taxonomic classification:

Protozoans

Metazoans

Lists of parasites by species:

Parasites of Dogs{3951}

Alimentary system:

Stomach and esophagus: Spirocerca lupi causes fibrous nodules in the wall of the esophagus and sometimes the stomach; Physaloptera and other spirurids may be found

Small intestine: Toxocara canis, Toxascaris leonina may be found in large numbers in puppies; hookworms including Ancylostoma caninum, A. braziliense, Uncinaria stenocephala; Strongyloides stercoralis are tiny and found in scrapings; Cestodes such as Taenia, Multiceps or Echinococcus; Dipylidium caninum has segments shaped like cucumber seeds; Mesocestoides and pseudophyllideans; Trematodes such as Alaria, Nanophyetus salmincola (salmon poisoning), and a few other species. Giardia.

Cecum and colon: Nematodes such as Trichuris vulpis (whipworm)

Liver and pancreas: trematodes such as Metorchis, a parasite of the bile ducts and gall bladder

Respiratory System

Nasal cavity and paranasal sinuses: Pneumonyssus caninum, a mite, and Linguatula serrata, a pentastomid.

Trachea and bronchi: Filaroides osleri, a rare parasite of the trachea, found in submucosal nodules; Capillaria aerophila, with typical lemon-shaped eggs

Lung parenchyma: adults of Filaroides milksi and Dirofilaria immitis (in pulmonary artery infarcts); larvae leave petechial hemorrhages, focal necrosis and nodular inflammation in the lungs which should be studied by the squash method because they will be much easier to identify than by histology (at least by Georgi!); larvae of Strongyloides stercoralis (filariform), Toxocara canis, Ancylostoma and a trematode, Paragonimus, are most common.

Cardiovascular system

Pulmonary artery and right heart: Dirofilaria immitis.

Mesenteric and portal veins: schistosomes, with the female enclosed in a groove in the male

Urogenital system

The kidney may contain Dioctophyme renale, a rare giant worm less than a meter long. In the bladder, Capillaria plica found partly or completely embedded in the mucosa.

Skin and hair

Sucking lice will be Linognathus setosus. Biting lice are probably Trichodectes canis, the intermediate host for Dipylidium caninum. Fleas are also intermediate hosts for D. caninum. Ticks include Rhipicephalus sanguineus or Dermacentor, the latter of which has brightly ornamented scutums. Mites include Sarcoptes (very pruritic), Demodex canis (non-pruritic), Cheyletiella yasguri causes mild pruritis on the back, or Otodectes cyanotis in the external ear canal.

Top of page

Parasites of Cats{3951}

Alimentary system

Stomach and esophagus: Gnathostoma, Physaloptera

Small intestine: Toxocara cati, Toxascaris leonina, Ancylostoma tubaeforme, A. braziliense, Uncinaria stenocephala, Strongyloides stercoralis, Trichinella spiralis (larvae may be seen as long thick clubs on Knott’s technique); cestodes include Taenia, Hydatigera taeniaformis (is this the old name for Taenia taeniaformis??) with the larval stage being Cysticercus fasciolaris of rodents, Echinococcus multilocularis, Dipylidium caninum, Mesocestoides; flukes are common because cats eat fish.

Large intestine: Strongyloides tumefaciens, Trichuris spp.

Respiratory system

Trachea and bronchi: Capillaria aerophila

Lung: Aelurostrongylus abstrusus found in gray nodules with small <9mm adults, eggs and first stage larvae; Paragonimus trematodes

Urogenital system

Capillaria plica, C. feliscati found in the bladder

Skin and hair

The biting louse is Felicola subrostratus. Cat fleas are either Ctenocephalides felis or C. canis and carry Dipylidium caninum. Mites are either Notoedres cati (highly contagious, pruritic, exfoliative, zoonotic dermatitis starting in the ears), Demodex cati on the edges of the eyelids, Cheyletiella spp. frequently found in cat feces, Otodectes cyanotis, or chiggers (Neotrombicula whartoni).

Top of page

Parasites of Rabbits{3951}

Alimentary system

Stomach: Obeliscoides cuniculi sheds typical strongyle eggs in the feces; Graphidium strigosum also found in the stomach.

Intestine: Strongyloides papillosus, Trichostrongylus retortaeformis, Nematodirus leporis, Eimeria

Large intestine: Passalurus ambiguus (5-11 mm long pinworms), Trichuris leporis, Entamoeba cuniculi, Trichostrongylus affinis

Liver and peritoneal cavity: Eimeria stiedae in bile duct epithelium, larvae of Taenia pisiformis called Cysticercus pisiformis

Urogenital system

Encephalitozoon cuniculi is found in the brain and kidneys, and may also affect guinea pigs. It must be differentiated from Toxoplasma.

Respiratory system

Pneumocystis carinii can cause respiratory disease in weanling rabbits. Protostrongylus boughtoni is another one.

Liver

Fasciola hepatica is readily transmitted to rabbits, and is found in the gall bladder and bile ducts. Bile duct hyperplasia is also a feature of Eimeria stiedae infection.

Connective tissues

Sarcocystis cuniculi causes white streaks in the muscle of Sylvilagus, not Oryctolagus.

Skin

Mites are usually Psoroptes cuniculi, grossly visible in the ear canal; other species might be Sarcoptes, Notoedres, Chorioptes, Cheyletiella parasitivorax, Listrophorus gibbus (laterally compressed mites that look more like fleas).

Top of page

Parasites of Rats{3951}

Alimentary tract

Stomach: Gongylonema neoplasticum

Small intestine: Trichinella spiralis, Nippostrongylus brasiliensis; Eimeria, Giardia

Large intestine: Syphacia muris, Heterakis spumosa (wild rats); Hymenolepis nana, H. diminuta

Liver

Capillaria hepatica, Cysticercus fasciolaris, Hepatozoon muris

Urogenital tract

Capillaria, Trichosomoides crassicauda with males living inside the females

Skin

Sucking lice are Polyplax spinulosa. Fleas are Xenopsylla cheopis. Mites are Ornithonyssus bacoti, Radfordia ensifera, Notoedres muris.

Top of page

Parasites of Mice

Protozoa: Invasive: Toxoplasma gondii, Sarcocystis muris, Klossiella muris, Encephalitozoon cuniculi, Pneumocystis carinii; Noninvasive: Giardia muris, Spironucleus (Hexamita) muris, Tritrichomonas muris, Eimeria falciformis, Cryptosporidium muris, Entamoeba muris{3551}

Helminths: Syphacia obvelata, Aspiculuris tetraptera, Hymenolepis nana, H. diminuta{3551}

Ectoparasites: Polyplax serrata, Myobia musculi, Radfordia affinis, Myocoptes musculinus, Psorergates simplex, Trichoecius romboutsi{3551}

Alimentary tract

Intestine: Giardia and many other flagellates

Small intestine: Pentatrichomonas and Spironucleus are flagellates found in the small intestine and crypts of Lieberkuhn. Eimeria muris in Europe is a common cause of diarrhea. Cryptosporidium parvum in the small intestine and C. muris in the stomach.

Large intestine: Aspicularis tetraptera, Syphacia obvelata, Heterakis spumosa, Hymenolepis nana, H. diminuta

Urogenital tract

Klossiella muris is an intracellular parasite in the kidney. Sporocysts found in urine. Very popular practical exam question, since they are so characteristic.

Skin

Mites are Myocoptes musculinus, Myobia musculi, Radfordia affinis, Psorergates simplex found in dermal nodules under the skin, Ornithonyssus bacoti. Sucking louse is Polyplax serrata.

Top of page

Parasites of Guinea pigs{3951}

Alimentary tract

Cecum and colon: Paraspidodera uncinata, the cecal worm; Hymenolepis nana; Eimeria caviae causes severe diarrhea and is found in thickened colon. Trichomonas caviae resembles Giardia but has only one nucleus.

Urogenital system

Klossiella cobayae is a renal coccidian of guinea pigs.

Skin

Biting lice are Gliricola porcelli, Gyropus ovalis, or Trimenopon hispidum. Mites are Chirodiscoides caviae, Campylochirus caviae and Trixacarus caviae (which is zoonotic).

Top of page

Parasites of NHPs{3951}

Alimentary system

Stomach: Nochtia nochti are bright red worms in the pre-pyloric region. Cross sections have 16 longitudinal cuticular ridges and channeled lateral alae. Gongylonema, Physaloptera, Protospirura, Physocephalus, Streptopharagus are spirurids that use insects such as cockroaches as intermediate hosts.

Small intestine: Strongyloides; S. fulleborni passes larvae instead of eggs in the feces; Oesophagostomum spp. and Ternidens deminutus are stout nodular worms whose larvae develop in the intestinal wall; Necator, Ancylostoma are hookworms; Globocephalus is a strongyle; Molineus, Trichostrongylus, Nematodirus are three trichostrongyles; Ascaris lumbricoides, Trichuris spp.; pinworms are Enterobius. Giardia duodenalis causes diarrhea. Entamoeba causes flask-shaped ulcers. Cryptosporidium parvum causes the same disease in infant macaques as in children. Schistosomes are found in thickenings of the intestine and bladder. Prosthenorchis are attached to the terminal ileum, and may cause abscesses, peritonitis and sepsis of callitrichids; this is a common and serious problem in wild-caught animals that is controlled by eliminating the Blatella cockroach intermediate host.{2765}

Large intestine: Hymenolepis nana is very small and Bertiella studeri is a large cestode. Prosthenorchis are large (55mm) thorny heads embedded in the wall and uses cockroaches and beetles as intermediates. Moniliformis is an acanthocephalan that is confused with a cestode because it is large (320mm) and pseudosegmented; it also uses cockroaches as an intermediate host. Cecum and colon of squirrel monkeys may contain Tritrichomonas mobilensis. Balantidium coli are large cysts that are heavily ciliated.

Liver

Capillaria hepatica deposits lemon-shaped eggs in the liver of many host animals, but the eggs develop into infective larvae only after the host dies and is ingested by a predator. Hepatocystis are in hepatocytes as meronts.

Pancreatic duct

Trichospirura leptostoma is a 10-20mm spirurid associated with chronic fibrosing pancreatitis.

Respiratory system

Nose and throat: Anatrichosoma, leeches, mites (Rhinophaga)

Lungs: Filaroides, Metathelazia, hydatid cysts, mites (Pneumonyssus simicola), Pneumocystis carinii.

Serous cavities

Dipetalonema are slender filariids free in the abdomen, sometimes trapped by local inflammation. Cysticercus tenuicollis and Mesocestoides are cestode larvae found either free in the abdomen or encased in fibrous tissue. Porocephalus, Armillifer, Linguatula are encysted on the gut surface. Prosthenorchis are encysted on all sorts of serous membranes in vertebrates.

Blood

Nematode microfilaria of Dirofilaria, Dipetalonema, Tetrapetalonema, Onchocerca, Loa, and Brugia are very hard to differentiate. Trypanosoma cruzi metacyclic forms on their way to cardiac muscle are C-shaped forms on blood smears. Plasmodium is common. Babesia can cause anemia in splenectomized animals. Adult schistosomes are found in large veins.

Muscles and connective tissues

The same filariids listed in the blood can also be found in the tissues or skin biopsies. Spirometra spargana, Mesocestoides, and Cysticercus are also found. Trypanosoma cruzi causes myocarditis by forming pseudocysts. Sarcocystis causes lesions in the tongue or esophageal muscles.

CNS

Cysticercus cellulosae

Skin

Sucking lice are Pedicinus and many other species. Anatrichosoma cutaneum causes nodules, edema of the joints, and long serpiginous blisters of the palms and soles. In addition, Dracunculus, Onchocerca microfilaria, and Dipetalonema may be found.

Top of page

Comments? Send an email to rodgers@uky.edu