Parasites by Host - Dog (Exam 5)

Exam 5 of Parasitology is Parasites by Host review, this is part 1 Dog. Blue text is testable material, black text is general info or potential extra credit. General note: Dr. Wu uses the class name Secernentea, but Modern genetic studies use name Chromadorea (Secernentea is deeply nested within Chromadorea, making them closely related in taxonomy. Secernentea is not considered a separate, co-equal class; it is now typically reclassified as the order Rhabditida under the class Chromadorea)

Thinking of all the parasites studied so far, What could be some differential diagnoses for an itching dog?

Sarcoptes

Ctenocephalides

Otodectes

Sarcoptes: morphological features

Arthropods > Arachnids > Acari > Astigmata > Sarcoptidae > Sarcoptes

Long, unsegmented pedicels

Anus on posterior edge of body

Sarcoptes causes what? (Disease/Clinical signs)

Causes mange in humans, dogs, foxes, horses, and cattle → Relatively host-specific, interspecies transmission uncommon

Burrow in tunnels under the epidermis → Begins in hairless areas (elbow, pinna), can progress to generalized

Causes Intense pruritus with papules, erythema, crusts, and excoriations develop, progresses to hyperkeratosis → Secondary bacterial infection common

Ctenocephalides: morphological features

Arthropods > Insecta > Siphonaptera (fleas) > Ctenocephalides

Genal and pronotal combs

Genal teeth run parallel to head

Which species of Ctenocephalides is more common: C. felis or C. canis?

Ctenocephalides felis

Ctenocephalides: how long does it take adults to emerge?

Eggs laid on host, fall off into environment

Adults emerge by weeks 3-4

Ctenocephalides is the intermediate host for what other parasites?

Intermediate hosts of tapeworm Dipylidium caninum and nematode Acanthocheilonema reconditum

Ctenocephalides: Disease

Can cause flea allergy dermatitis due to hypersensitivity

Can cause exsanguination of host (flea anemia)

Otodectes: morphological features

Arthropods > Arachnids > Acari > Astigmata > Psoroptidae > Otodectes > Otodected cynotis

Short, unsegmented pedicels

Where does Otodectes infest on host body?

Infests external ear canal and adjacent skin of dogs, cats, foxes, and ferrets, and sometimes humans

Otodectes: Disease/Clinical signs

Cause intense irritation, dark cerumen and tan flaky material in ear canal

Leads to head shaking that can cause aural hematomas

How would you treat a Sarcoptes infestation?

Sarcoptic mite treatments: Selamectin, moxidectin, fipronil, flumethrin, off-label isoxazolines

How would you treat a Ctenocephalides flea infestation?

Flea treatments: Isoxazolines (afoxolaner, fluralaner, lotilaner, sarolaner), nitenpyram, spinosad, selamectin, fipronil, imidacloprid, dinotefuran, flumethrin, indoxacarb

and Insect growth regulators (lufenuron, pyriproxyfen, methoprene) used to prevent development of larvae and pupae

Considering all of the parasites studied so far, what is a differential diagnosis for a vomiting dog?

Spirocerca lupi

Spirocerca lupi can cause what clinical signs?

Nematoda > Secernetea > Spirurida > Spirurina > Spirocerca > Spirocerca lupi

Mostly nonpathogenic

Can see dysphagia, coughing, and vomiting

Can cause aortic aneurysm or hypertrophic osteopathy

Can cause esophageal neoplasia (fibrosarcoma, osteosarcoma, chondrosarcoma)

Aberrant migration can cause neurologic signs

What features on this egg help identify it as Spirocerca lupi?

Small eggs with vermiform embryo passed in fecal flotation or sedimentation,

nodules on endoscopy

Considering all of the parasites we have learned so far, what are some differential diagnoses for a dog with diarrhea?

Cystoisospora

Giardia

Toxocara

Trichuris

Strongyloides

Cystoisopora: canine species

Protists > SAR > Apicomplexa > Coccidians > Cystoisospora

C. canis, C. ohioensis, C. burrowsi

How is Cystoisospora infection acquired?

Infection via ingestion of oocysts or paratenic hosts (in dogs and cats)

Cystoisospora clinical signs?

May cause diarrhea (hemorrhagic or nonhemorrhagic) in dogs (usually puppies)

Usually resulting from change of environment

Respiratory and nervous signs reported in some animals

How do you treat Cystoisospora infection?

Sulfadimethoxine

Giardia: what life cycle stage is infectious and not infectious?

Protists > Excavata (flagellates) > Diplomonadida > Giardia

Trophozoites can be passed in diarrheic feces but not considered infectious

Cysts are immediately infectious when passed

Giardia Assemblage C & D (Dogs): Clinical signs

Dogs may be subclinical

Puppies and debilitated dogs more likely to develop diarrhea

How is Giardia diagnosed and treated?

Diagnosis: Cysts on direct smear or fecal flotation with zinc sulfate, ELISA

Treatment: Metronidazole, fenbendazole

Toxocara canis: clinical signs

Nematoda > Secernetea > Ascaridia (roundworms) > Toxocara

Disease: Ill-thrift, pot-bellied appearance

Intestinal rupture or obstruction can occur

Toxocara: Diagnosis

Identification of adults in vomit or feces, eggs in fecal flotation

Toxocara: Treatment

Benzimidazoles, macrocyclic lactones, pyrantel, piperazine

Start as early as 2-weeks old in puppies, treat every 2 weeks to prevent environmental contamination

Trichuris: common name and species name for dogs

Nematoda > Adenophorea (Enoplida) > Trichinelloidea > Trichuris

Aka whipworms

Trichuris vulpis common among dogs in U.S.

Adults found embedded within wall of large intestine and cecum

Trichuris vulpis: clinical signs

Heavy T. vulpis infections can cause weight loss and diarrhea with mucus and blood

Trichuris: Diagnosis, Treatment

Prepatent period: 3 months in dogs

Diagnosis Lemon shaped eggs with bipolar plugs and a single cell on fecal flotation

Treatment: Macrocyclic lactones, benzimidazoles → Every month for 3 months

Strongyloides: species in dogs

Nematoda > Secernetea > Rhabditida > Strongyloides

Lives in mucosal crypts of small intestine

Strongyloides stercoralis: humans and dogs

Strongyloides: Modes of transmission

Transmammary transmission occurs in dogs, horses, pigs, and ruminants

Infection can be chronic due to autoinfection of larvae in Strongyloides stercoralis

Strongyloides: Diagnosis, Treatment

Diagnosis: L1 larvae in feces detected via Baermann

Treatment: Ivermectin, oxibendazole, levamisole, doramectin

Considering all of the parasites we have learned so far, what are some differential diagnoses for a client stating “there’ stuff in my dog’s poop”?

Cestodes

Acanthocephalans

Identify top cestode: how is infection acquired and diagnosed?

Dibothriocephalus latum

Infection: Plerocercoids in fish

Diagnosis: Whole tapeworm or long segment

Identify second cestode: how is infection acquired and diagnosed?

Taenia spp.

Infection: Cysticercus or coenurus in sheep and rabbits

Diagnosis: Square-shaped segments

Identify third cestode: how is infection acquired and diagnosed?

Mesocestoides spp.

Infection: Tetrathyridium in snakes, birds, and small mammals

Diagnosis: Small sesame seed-shaped segments

Identify bottom cestode: how is infection acquired and diagnosed?

Dipylidium caninum

Infection: Cysticercoids in fleas

Diagnosis: Pumpkin seed-shaped segments

What is the treatment for cestodes?

Praziquantel

How do hosts acquire Acanthocephalan infection?

AKA Thorny-headed worms → White, flattened body (become cylindric when placed in water)

Final host infected by ingesting arthropod or paratenic host

Dung beetle for Macracanthorhynchus hirudinaceus

Millipede for Macracanthorhynchus ingens

Acanthocephalans: Diagnosis, Treatment, Clinical Signs

Usually asymptomatic in dogs

Diagnosis:Thick, multilayered eggs with a dark brown shell on fecal flotation or sedimentation. Adults can be passed in feces

Treatment:No approved treatment in dogs

Considering all of the parasites we have learned so far, what are some differential diagnoses for a sneezing dog?

Pneumonyssoides

Eucoleus