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114.e2 Baylisascaris Infection

Baylisascaris Infection
VetBooks.ir Initial Database

signs as early as 9-10 days after ingestion of
BASIC INFORMATION
raccoon feces containing ova with infective • CBC: possible eosinophilia
Definition larvae. • Serum biochemistry profile, urinalysis: to
A rare but potentially devastating zoonosis • Signs often progress rapidly over several days. rule out toxic or metabolic diseases
involving parasitic infection with the raccoon • Complete neurologic and ocular examina-
roundworm, Baylisascaris procyonis PHYSICAL EXAM FINDINGS tions: asymmetry of deficits is expected if
• NLM: depression, ataxia, head tilt, circling, any deficits are present
Synonyms nystagmus, opisthotonos, recumbency, coma • Fecal flotation and examination: more than
Baylisascariasis, ocular or neural larval migrans; • OLM: blindness, signs of uveitis (e.g., red 20 dogs in the Midwest have been shown
raccoon roundworm, visceral larval migrans eye, photophobia), observable larvae within to have a mature intestinal infection of
the eye/retina Baylisascaris with infective eggs shed in their
Epidemiology • VLM: usually an incidental finding without feces
SPECIES, AGE, SEX clinical signs • Cerebrospinal fluid tap with cytology:
• Raccoons are the natural hosts for the mature meningoencephalitis with increased eosino-
enteric parasite. However, larval stages of B. Etiology and Pathophysiology phils
procyonis can infect more than 90 species of • Eggs of B. procyonis become embryonated
birds and mammals, including dogs. and infective (contain infective second-stage Advanced or Confirmatory Testing
• Cats appear to be only marginally susceptible larvae) 24-48 hours after being passed by Virtually never performed in small animal
or even resistant. the raccoon. Infective eggs are highly stable medicine, given the rarity of clinical disease in
and may remain viable within the environ- dogs and cats
CONTAGION AND ZOONOSIS ment for years; however, they can be • MRI (brain): preferential destruction of white
• Zoonosis occurs through the fecal-oral route. destroyed by extreme temperatures. matter
Exposure to aged raccoon feces harboring • All animals (including dogs and humans) • Serologic testing is available for humans but
embryonated B. procyonis eggs (e.g., in are infected by ingesting the embryonated/ is not commercially available for pets.
uncovered outdoor sandboxes or similar larvated eggs. Raccoons originally become • Definitive diagnosis may only be possible
raccoon latrines) is a major risk factor for infected in the same manner or by ingesting postmortem.
human infection (fatal meningoencephalitis). paratenic hosts.
Children younger than 2 years are at highest • Once ingested, the larvae emerge from the TREATMENT
risk. eggs within the host’s intestine and begin to
• Dog feces also contain Baylisascaris eggs when migrate (larva migrans) through the liver, Treatment Overview
the dog is infected with intestinal adult B. lungs, brain, and eyes as early as 3 days after It is critical to remove all adult stages of this
procyonis. infection. parasite from the small intestine of an infected
• The tissues of transport or paratenic hosts • Migration of only one or two larvae through dog with anthelmintic therapy before treat-
(e.g., small rodents) may contain encysted/ the brain can cause destruction of the white ing neurologic signs with glucocorticoids.
arrested second-stage larvae. If a raccoon or matter (leukomalacia) and severe inflamma- All feces should be removed promptly from
other suitable mammalian host (e.g., the tion and necrosis. the cage or kennel and properly disposed
dog) ingests this infected transport or of. Gloves should be worn at all times when
paratenic host, the ingested larvae will excyst DIAGNOSIS there is contact with infected feces. Hand-
and migrate, thus infecting the gut (or other washing is essential. The therapeutic goal is
host tissues) of the definitive host. Diagnostic Overview rapid identification and treatment to prevent
Infection with B. procyonis is of great public progression of leukomalacia and neurologic
GEOGRAPHY AND SEASONALITY health significance. If humans become infected signs.
• More common in California and the mid- with NLM, the consequences can be fatal. B.
western and northeastern United States procyonis rarely poses a significant threat to Acute General Treatment
• Infected raccoons have also been reported dogs. • Anthelmintics: when Baylisascaris eggs are
in Louisiana, Georgia, and Florida. found incidentally on a fecal flotation
Differential Diagnosis ○ Albendazole 50 mg/kg PO q 24h × 10
Clinical Presentation Signs of central nervous system dysfunction days or more: traditionally the anthelmin-
DISEASE FORMS/SUBTYPES due to Baylisascaris infection in dogs and tic of choice. Administration for > 3 days
• Clinical illness due to B. procyonis is extremely raccoons are not common. Causes that are much may risk myelosuppression.
uncommon in dogs; neurologic and ocular more common include ○ Milbemycin oxime 0.5-1 mg/kg PO: B.
signs are theoretically possible. Rather, the • Other infectious causes of encephalitis: procyonis infection is a newer application
greatest concern is regarding the zoonotic toxoplasmosis, tick-borne diseases, Neospora, of this treatment; ≈75% effective at
potential of B. procyonis eggs passed in canine distemper virus, rabies eliminating Baylisascaris infection in dogs
raccoon or (rarely) canine feces. • Granulomatous meningoencephalitis (GME), with 1 dose.
• In humans, visceral larval migrans (VLM), necrotizing meningoencephalitis (NME), • Neurologic larva migrans (rare in dogs and
ocular larval migrans (OLM), and neural eosinophilic encephalitis (EE), necrotizing cats): glucocorticoids (e.g., dexamethasone
larval migrans (NLM) may be observed. leukoencephalitis (NLE), and menigoen- 0.1-0.2 mg/kg IV q 8-24h) are essential to
cephalitis of unknown origin (MUO) stabilize the inflammatory component of
HISTORY, CHIEF COMPLAINT • Toxin exposure encephalitis.
• Dogs infected with B. procyonis generally • Neoplasia • Ocular larvae within the retina may be killed
show no clinical signs. Rarely, dogs may • Metabolic disease (e.g., hepatic encephalopa- using laser photocoagulation or removed by
sustain larva migrans that causes overt clinical thy, hypoglycemia) enucleation.

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