Onchocerca lupi

Onchocera lupi in Dogs:
An Emergent Zoonotic Disease
• Matthew Chavkin DVM, MS, DACVO
• Veterinary Referral Center of Colorado
• mchavkin@vrcc.com
Onchocerca lupi - 2011
Surgery
Accola PJ et al. JAVMA 2006; 2229; 220-225
Surgery
Tightly coiled bundles of worms surrounded by collagenous or granulomatous
Inflammation intimately associated with the sclera, extraocular muscles and
orbital fascia.
Surgery
Onchcerca lupi
adult
worms
microfilaria
L4
black fly L1-L3
L1-L3
Onchocerca Life Cycle
110 μm
tooth
bent tail
Males 5 cm
Female 10-20 cm?
Simulium bites the skin of the dog over the dorsum, not the eye
Clinical Disease
Episcleral Granuloma due to Adults
and possible local microfiliaria
Microfilaria in the skin are largely
benign
Many subclinical cases
Often discovered as an incidental
finding or inflammation after
immiticide treatment for
heartworm
Increasing Prevalence
• My first case was in 2011
• 2 more cases in 2011
• 1 case each month in 2014 & 2015
• All dogs are rescues from New Mexico
• First case in Farmington was in 2006
Geographic Distribution of Onchocerca
lupi in Dogs
Challenging Diagnosis
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Examination Findings; Originally from NM
Episcleral biopsy – grossly visible adult worms
Histopathology – granulomatous, eosinophilic
Ultrasound, CT, MRI
Skin snip for microfilaria
No serologic testing available
Otranto 2013
Spectrum of Clinical Disease in Dogs
New Mexico
Treatment – Current Recommendation
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Clinical Suspicion – history, examination
CBC, chemistry profile, UA, Heartworm Ag
Oral/topical corticosteroid
Incisional Biopsy (worms in 70% ethanol)
Test dose of Ivermectin 50 μg/kg PO once
Toxicity- transient mydriasis, salivation, ataxia
• Doxycycline 10 mg/kg/day PO for 3 months
• Ivermectin 200 μg/kg PO once monthly for 6
months
• Lifelong monthly ivermectin 6 μg/kg PO
Zoonotic Potential
2013 First reported human
case of Onchocerca lupi in US
22 month old Navajo
child from Arizona
Eberhard ML. Am J Trop Med Hyg 2013; 88; 601-5
O. lupi Zoonotic Potential
Prof Domenico Otranto DVM, Phd, Dip.EVPC, FRES
Dept Vet Med, Univ of Bari, ITALY
Otranto et al., Am J Trop Med Hyg. 2011 84:55-8
Otranto et al., Parisit Vectors. 2012 5:84
O. lupi Zoonotic Potential
• Canty PT et al. The emergence of zoonotic Onchocerca lupi
infection in the United States – a case series. Clin Inf Dis. 2015
• 6 human cases since 2013
• Primarily nonocular sites for adult worms: SQ, orbit, spinal
• Gravid female worms
• Resided in Arizona, New Mexico, Texas, travel to Colorado,
Utah
• All patients recovered after treatment with doxycycline for 6
weeks; neurosurgical intervention was necessary (dx/tx) for
patients with spinal involvement
Challenges
• O. lupi is difficult to diagnose, especially in the
early stages of infestion. Future tissue PCR is
likely.
• 6 month prepatent period makes early diagnosis
difficult
• 300 + dogs are transported monthly from
Northern NM to CO for forever homes.
• The prevalence of O. lupi infestion in transported
dogs is unknown (~25% of adult dogs)
Challenges
• No standardized health screening for
transported dogs
• The dogs originate from an area of limited
veterinary care.
• Simulum tribulatum PCR + for
O. lupi in ABQ and San Gabriel Valley
• It is unknown whether we have the fly vector
in the Denver Area
Recommendation
• All dogs transported from New Mexico and
Arizona to Colorado should receive a
heartworm test and be placed on year-round
microfilaricide (heartworm prevention) to
render them noninfectious to other dogs and
people.
Questions?