Raccoon roundworm: Baylisascaris procyonis

Helminthic worms and One
Health
Sydney Patricia Rudko
What is a Helminth?
• The term “helminth” actually refers to various species from multiple
taxa
• Taxa include: Trematodes (flatworms), nematodes (roundworms),
and cestodes (tapeworms)
• Share a common set of characteristics, notably they are parasitic, egg
laying, and have larval and adult stages.
Photos CDC DPDx
Global distribution of soil-transmitted
helminth infections
Thiswormyworld.org
Parasitic infection in North America
DOI: 10.1371/journal.pntd.0000256, Peter Hotez Neglected Infections of Poverty in the United States of America
In Canada..
Study published in 2014 looking at parasite prevalence in the Canadian arctic.
doi:10.1016/j.diagmicrobio.2013.08.026 Seroprevalence of parasitic zoonoses and their
relationship with social factors among the Canadian Inuit in Arctic regions
-You’ll only see what you look for.
-Currently in Alberta or Canada there are no helminthic worm parasites on the
Alberta or Canadian notifiable disease registries.
Parasitic zoonoses
• Parasites often have a co-evolutionary
relationship with their host, this makes them
unique compared to bacteria or viruses
• Parasites exist all around us!
• Despite this evolutionary relationship,
helminthic zoonoses occur. Nematodes
specifically have been shown to switch
hosts more frequently than other
helminths.
Lieutenant Jadzia Dax, a Trill on Star Trek: Deep Space
Nine. Jadzia hosts the symbiont Dax
Nematode lifecycles are taking place
all around us.
•
•
•
115 described human-parasitic nematodes
(roundworms) but ~ 5000 wildlife
nemtodes which may or may not have
zoonotic potential
“When such [nematode] zoonoses infect
humans it is usually as a consequence of
human influence or activity
(anthropogenic).”
Many ways this can occur: socioeconomic
factors, habitat encroachment, livestock,
climate change, hunting.
R.C.A. Thompson / International Journal for
Parasitology 43 (2013) 1079–1088
Case study: Baylisascaris procyonis
• Raccoon roundworm
• Prevalence between 70-90% in Raccoon populations
• Infected raccoons may shed hundreds to thousands of Ova
each day.
• Raccoon latrines
CDC DpDx
CDC DpDx
Human health
• Larvae hatch in the intestine and begin to migrate
through tissues. May migrate to the eye or brain
• Few human cases (n=18), but most fatal/severe
disabilities
• Due to proximity of raccoons and humans, and high
prevalence of B. procyonis in raccoons (82% in
adults, 90% in juveniles) and number of eggs shed
(≈20,000 eggs/g of feces ) considered a serious
potential zoonoses.
Prevalence in Winnipeg
PMCID: PMC2711470
Not just a human problem! Ascarid ova are notoriously environmentally resistant! Soil and
water contaminated will remain infective.
Environmental persistence
• Eggs have been shown to remain viable for up
to 6 months at temperatures between -15C –
62C.
• Freeze thawing does not affect viability
• Dry, desiccated eggs remain viable for up to 7
months
• Chlorination is ineffective at killing.
Animal health
• Baylisascaris procyonis larvae also infect
animal species (90-130 species described)
• Small mammals like rabbits, woodchucks and
mice are the natural intermediate host.
Baylisascaris and Allegheny wood rats
-Neotoma magister
-Threatend species
-Has been extripated from NY and
NJ.
-Cause of extripation is a bit of a
mystery.
Three major hypotheses to explain
decline
• 1. habitat fragmentation
• 2. the food-decline hypothesis
• 3. B. procyonis, the parasite hypothesis
– Baylisascaris causes severe neurological disease in
these rats. More so than other rodent species.
– As foragers, the woodrat may bring contaminated
food to its den. Also may bring home raccoon feces
– Raccoon populations are booming in areas of
extirpation
Wood rat survival is poor where
contamination with B. procyonis ova is
high
http://www.jstor.org/stable/3095292
Why did this occur?
• Changes in geographical distribution/habitat
loss and changes in foraging have resulted in
the wood rat being in contact with raccoons
more often.
• The co-evolutionary relationship between
intermediate host and worm does not exist in
this case
To conclude
• To understand
parasitism in the
environment and
understand risk
to wildlife, or
human health,
we need One
Health.
For further study
• “How do humans affect wildlife nematodes?”
Trends in Parasitology. (2015) 1–6.
• “Baylisascaris procyonis: An Emerging
Helminthic Zoonosis.” Emerging Infectious
Diseases. (2002) 8:4.
http://wwwnc.cdc.gov/eid/article/8/4/pdfs/01-0273.pdf
• “Parasite zoonoses and wildlife: One health,
spillover and human activity” IJ Para. (2013)
43:12-13.