Parasitic Diseases Lecture

Sarcoptic Mange
Sarcoptes scabiei mite
~1/64 of an inch long
Pearly white and oval-shaped
Spines on bodies
Year-round; winter
Humans ("scabies"), canids,
felids, bears, mustelids
Common in red fox, wolves,
and coyotes in N. America
impacts on younger animals
Highly contagious, direct
transfer of mites at any stage
of their development
Indirect transfer of mites
(mechanical transfer) –
Sarcoptic Mange
• Highly specific to host type,
• Life cycle completed in
burrows within epidermis of
• Adult mites mate in small
pockets near the surface of
• Hatched larvae pass through a
nymphal stage and continue
migration through epidermis,
becoming adults within 2
Sarcoptic Mange
Female mites burrow into skin of
host; use jaws and front legs to cut
Female lays 2-3 eggs each day, up
to 2 months
Larvae hatch, 3-4 days
Crawl onto surface of skin, use hair
as shelter
Both larvae and adults eat skin cells
from hosts
Sarcoptic Mange
Oily skin, crusting, hair loss, scab
Lesions - physical damage to skin,
irritation caused by parasite
excretions, and allergic response of
Hair loss in characteristic patterns
Poor body condition, listlessness,
abnormal behavior, increased
May ultimately die from complications
with mange infection or exposure;
Sarcoptic Mange
• Trichodectes canis
• Dog biting louse
• 2ndary infection
Sarcoptic Mange – WI Wolves
1st identified in a Great Lakes
wolf, 1991
Since 1991, signs of mange
detected in 27% of wolves
High of 58% in 1992-1993
1993 = 11% decline in wolf
Some literature suggesting
population impact most severe in
2nd or 3rd year of epidemic
Impacts on annual pup survival?
• Ixodes (e.g., deer tick;
Lyme disease
(Borrelia burgdorferi)
• Dermacentor (Am.
Dog tick & Rocky Mtn
wood tick); Rocky
Mountain spotted
fever (Rickettsia
rickettsii )
• Amblyomma (e.g.,
lone star tick;
Ehrlichiosis (Ehrlichia)
Winter tick
(Dermacentor albipictus)
Winter tick
(Dermacentor albipictus)
• Moose begin grooming in
Jan (nymph stage) –
mechanical and/or
immunological irritation
• Extensive grooming
through Mar-Apr = destroy
winter coat
• Severe hair loss = gray
coloration (undercoat) =
"ghost moose".
Nasal Leeches
Leech (Genus Theromyzon) feeds
directly on blood from nasal
passages, trachea and mucous
membranes of eyes
Spring/summer - leeches actively
seeking potential hosts and
Dabbling ducks (e.g., mallard,
teal, wigeon, northern shoveler,
etc.) and swans
Nasal Leeches
• Protruding from nares or
attached externally
• Resemble small sacks of blood
• Birds vigorously shaking
heads, scratching bills or
• Nasal and respiratory tract
infestations = labored
breathing and gaping (similar
to aspergillosis infection)
Nematodes = roundworms
Complete digestive systems
Most species dioecious
2 main categories
eggs are infective
larva are infective
Gizzard Worm
• Parasitic nematode
• Genus Amidostomum
or Epomidiostomum
• 10-35 mm, coiled,
thread-like roundworm
• Beneath surface lining
and grinding pads of
• waterfowl
Gizzard Worm
Gizzard Worm
• 1st exposure on breeding
• Large worm burdens;
reduce vigor, couple with
migration, etc…
• No field signs
• Poor growth/weight gain
in young birds?
• Emaciation, general
• Poor digestion
Raccoon roundworm - Baylisascaris procyonis
Raccoon roundworm - Baylisascaris procyonis
Life cycle is
direct or indirect
depending on
age of raccoon
Definitive host
Raccoon roundworm - Baylisascaris procyonis
Adults in intestines
lay eggs
Raccoon roundworm - Baylisascaris procyonis
Eggs are shed
with feces
Raccoon roundworm - Baylisascaris procyonis
Eggs are shed
with feces –
loads of ‘em
Raccoon roundworm - Baylisascaris procyonis
outer coat
Raccoon roundworm - Baylisascaris procyonis
Over 2-4 weeks the
eggs develop larvae
Raccoon roundworm - Baylisascaris procyonis
Can remain
infectious for
Raccoon roundworm - Baylisascaris procyonis
Embryonated egg
with larvae is
ingested by young
raccoon -- Direct
Raccoon roundworm - Baylisascaris procyonis
Egg hatches
in to larva
Raccoon roundworm - Baylisascaris procyonis
Larvae in
intestines develop
into egg-laying
Infection rates in
raccoons are
high – as high
as 70% of adults
and over 90% of
Raccoon roundworm - Baylisascaris procyonis
egg with larvae
are ingested by
Raccoon roundworm - Baylisascaris procyonis
Eggs hatch and
release larvae into
intestines  gut
wall  migrate
thru the various
tissue (larval
migrans) causing
damage and then
Raccoon roundworm - Baylisascaris procyonis
In the eye 
Raccoon roundworm - Baylisascaris procyonis
5-7% CNS disease
Raccoon roundworm - Baylisascaris procyonis
Dead intermediate
is scavenged by
adult raccoon –
Raccoon roundworm - Baylisascaris procyonis
Raccoons are ubiquitous in
U.S. and urban adapted
Raccoon roundworm - Baylisascaris procyonis
Definitive host??
An emerging zoonotic
especially of young children
•Contact with raccoon feces
•Young age (less than 4)
•Developmental delay
•At any age – anyone exposed to raccoon feces – researchers, wildlife
rehabilitators, etc – asymptomatic or subclinical, sometimes ocular migrans or
•Aggressive migration of larvae
•Molt and grow as migrate
•Only 5-7% enter neural (or ocular) tissue – induce an inflammatory
(eosinophilic) response  encephalitis
•Migrate extensively in brain before being walled off by host
•Post-inflammatory atrophy, necrosis, and impairment
Very distinctive
prominent alae
excretory columns
•Encephalitis in an 11-month-old boy.
• Abnormal high signal throughout most of
the central white matter (arrows)
compared with the dark signal expected
at this age (broken arrows).
• Extensive evidence of raccoon activity
and fecal contamination, including 21
latrine sites, were identified on the
patient’s property and the adjacent
vacant lot.
• 11 raccoon were necropsied, all were
Raccoon Roundworm
-Single adult female worm = 115,000 to 877,000 eggs per
-raccoon infected with multiple worms = shed up to
45,000,000 eggs daily
Raccoon Roundworm
midwestern U.S. documented in 68–82% of raccoons; >90% juveniles
Raccoon Roundworm
- Prevalence, intensity of infection, avg # of larvae significantly higher in the highly
fragmented landscape
- Probability of infection, intensity of infection, and avg # of larvae per mouse per
patch varied as functions of forest patch area and isolation (DD)
Raccoon Roundworm
A study conducted in Northern California tried to determine if a pattern
existed to the preferred location of latrines. While latrines on the ground and
on roofs appeared to be the most favorable, preferences varied by location.
Raccoon Roundworm
• Percentage of California properties that contained at least one
raccoon latrine positive for Baylisascaris procyonis eggs (number of
properties = 164).
Raccoon Roundworm
- Eggs ~ 65 microns in size
- Household disinfectants (bleach) will not kill
(remove coating)
- Fire/heat, boiling water, required to kill eggs
Raccoon Roundworm:
Trophic-level Effects
• Former range of the
Allegheny woodrat
(inside bold line),
and regions where
woodrats have
disappeared in
recent decades
(stippled areas).
Raccoon Roundworm:
Trophic-level Effects
• Range of raccoon
roundworm in
Allegheny woodrat