Protozoan Parasites:
Lecture 19 - Coccidia Part II & Cryptosporidium
Pages 29-38
Coccidia:
Life cycle & treatment effectiveness?
Asexual
stages
Sexual
stages
Prophylactic drugs
Current drugs only work on
asexual stages outside of
host cells
Sanitation : within 24-48 hours
i.e. before oocysts are mature &
infective (sporulated oocyst)
Supportive therapy
- No current drugs
kill/target sexual
stages in cells
Avian Coccidiosis
Chickens - 9 species of Eimeria
• Eimeria acervulina
–
–
–
–
Most common
Mildly pathogenic
Upper small intestine
Prepatent period: 4-5 days
• Eimeria tenella
– Most pathogenic (high mortality)
– Cecum
– Prepatent period: 7+ days
Pathogenesis
• Site of infection
• Small intestine to cecum
depending on species involved
• Intestinal / cecal lesions range
from minor to round, white/grey
plaques to severe necrotic cores
& hemorrhage with significant
blood loss
Clinical signs
• Bloody droppings & hemorrhagic
diarrhea beginning 4 days post
infection
• Acute death
– High mortality rates
• Emaciation, pallor & inappetence
Control &Treatment
• $ 700 million/year loss
• Isolate sick birds - treating sick birds is
futile
• Treat healthy birds with anti-coccidial
medications
• Preventative (prophylactic) medication
in feed
– Ionophores (monensin, salinomycin,
lasalocid)
– Amprolium
– Decoquinate...
• Resistance is widespread
– Rotate drugs or use "shuttle" program
Control &Treatment
• Vaccines have been developed but
problems with administration
– Injectable
– Nebulizer/sprayer
– Feed additive
• Raise young chickens separate from
older birds (segregation of industry)
• Proper hygiene/sanitation
Avian Coccidiosis
• Turkeys
– 7 species of Eimeria infect turkeys
– E. adenoeides, E. gallopavonis, E. meleagrimittis
are all pathogenic
– Lesions < than in chickens, but mortality rates high
in young birds
• Ducks & Geese
– Renal coccidiosis - Eimeria truncata
– Intestinal coccidiosis - E. anseris
Bovine Coccidiosis
13 species infect cattle in North America
• Eimeria zuernii & Eimeria bovis
– Most pathogenic
– Mixed infections are the rule
• Calves
– Most susceptible
– 3 weeks to 6 months of age,
• Typically 2 - 6 months
– Also older calves housed in groups
• First generation meronts (first
asexual replication stage) grow
to giant size & produce
thousands of merozoites
– E. bovis - endothelial cells of
lacteals in the villi
– E. zuernii - lamina propria of the
ileum
• Prepatent period: 12-24 days
Bovine Coccidiosis
Clinical signs
• Moderate infections:
– Diarrhea, listlessness, anorexia
Clinical signs
• Severe infections:
– Explosive liquid bloody
diarrhea, emaciation &
tenesmus
– Hind quarters of calf can
become soiled with feces
– Secondary infections
common
• Pneumonia…
– Calves that don’t die in 710 days will usually recover
Eimeria bovis
Summer Coccidiosis
• Calves 3-6 months
– Stress - first time on pasture
– Older cows carriers & infect
the pasture
– Warm temperatures & high
humidity
– Diarrhea to dysentery
– Tenesmus & projectile feces
• Dehydration & death if
untreated
Eimeria zuernii
Winter coccidiosis
• Diarrhea & tenesmus
• Severe cold weather
• Stress factors
– Weaning, shift from
pasture to feedlot
Eimeria zuernii
Nervous coccidiosis
• Acute diarrhea
• Muscular tremors, convulsions,
blindness
• 50% mortality
– Pathogenesis is not
understood but majority of
cases occur during coldest
months (stress?)
Control & Treatment
• General prevention:
– Reduce stocking rates,
minimize stress, clean housing
& feed
– Pasture management?
– Provide adequate colostrum
• Treatment & prevention?:
– Decoquinate, amprolium,
monensin, sulfamethazine,
sulfaquinoxaline, lasalocid
Control & Treatment
• Outbreak:
• Sick calves
– Isolate & provide supportive
therapy & fluid replacement
• Healthy calves
– No clinical signs = treat with
anti-coccidial drugs
• Clean & sanitize
– Housing between groups of
calves
– Hot & dry = kills oocysts
• Do not mix calves of different ages
• Reduce stress
Ovine Coccidiosis
12 species of Eimeria infect sheep
prepatent period ~ 14 days
• Lambs in feedlot or after shipping
– 12-21 days after arrival
– Watery diarrhea for several
days-2 weeks
– Depression, inappetence
followed by weight loss
– Mortality usually <10%,
• But significant weight loss
can occur
– Soiled wool leads to Fly strike
(myiasis)
Caprine Coccidiosis
6 species of Eimeria infect goats prepatent period ~ 14 days
• More susceptible than sheep
• Clinical signs of diarrhea typically
follow weaning
• Heavily infected
– Usually die
– Recovered kids may fail to grow
normally
Ovine / Caprine Coccidiosis
• Control & Treatment
– As in cattle
– Raise lambs on slatted floor pens
– Good sanitation
Equine Coccidiosis
• Eimeria leuckarti
• Coccidiosis is rare in
horses
– Few reports of
diarrhea or weight
loss in infected
horses
micropyle = exit pore
Oocyst with prominent micropyle
Rabbit Coccidiosis
• Eimeria stiedae
• Liver
– Bile duct epithelium
– Biliary hyperplasia & cirrhosis
resulting in diarrhea
– Often subclinical
– Young rabbits most susceptible
– Anorexia, weight loss, distended
abdomen, icterus & rough hair
coat
– Sudden death - infrequent
Rabbit Coccidiosis
• Eimeria intestinalis &
– Crypts of small intestine
• Eimeria flavescens
– Cecum
• Often subclinical
• Anorexia, weight loss, &
rough hair coat
• Denuding of the epithelium
& severe diarrhea
• Death
Control & Treatment
• Prophylactic administration of
sulfonamides or lasalocid
• Reduce stress
– Intestinal form occurs even in
well cared for bunnies
• Prevent contamination of feeders,
waterers, cages, hutches...
• Proper management
Swine Coccidiosis
• Isospora suis
– Severe disease in nursing
piglets
– Post 1960's
– Wherever pigs are farrowed in
confinement
– 15-20% of piglet diarrhea
Swine Coccidiosis
• Isospora suis
– Enterocytes of the small
intestine & occasionally
cecum & colon
– Prepatent period 4-5
days
– Patent period 2 weeks
Clinical signs
• Piglets 1-2 weeks
– Yellow- grey pasty diarrhea
• Diarrhea smells like "soured milk“
• Blood not present unless other
disease agents involved
– e.g. rotavirus
• Depressed weight gains, high
morbidity, moderate mortality
Clinical signs
• Piglets 5-6 weeks
– Post-weaning
diarrhea
• Depressed weight gains,
high morbidity, moderate
mortality
Control & Treatment
• Anti-coccidials are not effective
• Nursing piglets do not eat or drink
enough for drugs added to feed or
water to be effective
• Sanitation to reduce the number
of infectious oocysts in
environment
• Reduce stress
Canine Coccidiosis
• Isospora canis
• Largest oocysts in dogs
• Lamina propria of distal small
intestine & may cause
diarrhea associated with
weaning stress
– Concurrent bacterial or
viral infections?
Canine Coccidiosis
• Isospora ohioensis complex
• I. ohioensis, I. burrowsi & I. neorivolta
– All have small oocysts
– Enterocytes in the small intestine,
cecum & colon
– Diarrhea in puppies is:
• Associated with stress
• Concurrent bacterial or viral
infections?
Feline Coccidiosis
• Isospora felis &
Isospora revolta
• Develop in the
enterocytes of small
intestine & can
cause diarrhea &
enteritis in kittens
• Newborn - 4 weeks
old
• Stress factors likely
involved e.g. other
disease agents
• Rare unless other
disease agents
present
Isospora revolta
Isospora felis
Canine & Feline Coccidiosis
• Paratenic hosts
– Infections in dogs & cats can be
acquired through a paratenic
host
– Mice, cattle, sheep & other
herbivores
– Ingest the oocysts & sporozoites
invade the extra-intestinal tissue
• Mesenteric lymph nodes,
brain, muscle
– Sporozoites become encysted
within tissue & are released
when ingested by cats or dogs
Canine & Feline Coccidiosis
• Control & Treatment
– Sanitation to reduce exposure to oocysts
– Ensure sufficient colostrum
– Reduce stress
– Reduce opportunity for hunting
• Re: paratenic host
– Clinical cases
• Supportive therapy
• Sulfonamides or amprolium to reduce patent period?
– Value?
– Response to treatment is seldom dramatic
– Treatment of dams prior to parturition ?
Super ‘Role’ Model
• Barbie says,
“Prompt disposal of
feces is the key to
controlling
coccidia!”
Cryptosporidiosis
Zoonosis
• "Coccidian-like" parasite of the Genus Cryptosporidium
– Many species
• Infect the microvillous region of epithelial cells lining
the gastrointestinal & respiratory tracts of many
different vertebrates
• Intracellular, extra-cytoplasmic parasites of epithelial cells
Cryptosporidiosis
• Mammals
• Cryptosporidium parvum
– Infects small intestine
– Cats, dogs, horses, cattle & humans...
– Very important cause of neonatal
diarrhea in calves
– Zoonotic
• Cryptosporidium hominis
– ONLY Infects small intestine of humans
– Causes diarrhea
Cryptosporidiosis
• C. andersoni
– Infects the abomasum of
ruminants (cattle)
• Older calves (>1 month) &
mature cattle
– May lead to sub-par
performance in cattle
– Milk production & weight gain
– Life-long infections?
Cryptosporidiosis
• C. bovis
– Found in the small intestine
– Primary infection in postweaned cattle
– BUT: No clinical signs
– Life-long infections?
– Morphologically identical to
C. parvum, therefore
confounder...
Cryptosporidiosis
• C. suis
– Morphologically identical to
C. parvum
– Small & large intestine of
swine
– ‘Host adapted’ -infects pigs
of all ages
– No clinical signs
• One report in humans
– Life-long infections?
Cryptosporidiosis
• Birds
• C. baileyi
– Respiratory tract & cloaca
of chickens & turkeys
• C. meleagridis & C. galli
– Small intestine of chickens
& turkeys
Cryptosporidiosis
• Reptiles
– Cryptosporidium serpentis
• Intestinal infections
• Fish
– Cryptosporidium molnari
• Intestinal infections
Morphology
• Sporozoites, Merozoites, Meronts &
Gamonts
– Similar to coccidia
• Oocysts
– C. parvum - round & very small 4-6 um
– C. andersoni - slightly larger 6-8 um
– All are sporulated when passed in feces
– Immediately infective
– Oocysts contain 4 "naked" sporozoites no
sporocysts
Source: CDC
Cryptosporidium life cycle
Epidemiology
Transmission
– Oocysts
• Immediately infective, highly
resistant & remain viable for
months
• Standard disinfectant
concentrations fail to kill
– Ethanol, methanol, sodium
hypochlorite, isopropanol...
• Methods that “work”
– 6% hydrogen peroxide
– VIM
– High pressure steam
cleaning...
Epidemiology
Transmission
• Direct: fecal-oral route is common in confinement
Epidemiology
Transmission
• Waterborne
outbreaks are the
most common source
for human infections
Epidemiology
Transmission
•
•
•
•
•
•
•
•
Milwaukee - 1993
Kelowna & Cranbrook – 1996
Chilliwack – 1998
North Battleford -2001
Kamloops – 2002
Kansas – 2003
Wausau Wisconsin-2007
Globally, many every year...
Epidemiology
Prevalence
• Worldwide
• Infections common
– Young animals, neonates & immunocompromised
• Dogs & Cats
– Reported prevalence of 5-10%
– Underestimated...
Epidemiology
Prevalence
• Livestock
– Prevalence up to 100% in
calves
– Calves <3 weeks of age &
co-infection rotavirus,
coronavirus & E. coli
– Dairy > Beef feedlot > Beef
on range
– Calves: prepatent period is
4-6 days, patent period 714 days
– Canadian survey
• 17% of horses
• 11% of pigs
• 23% of sheep
ON PEI
Beef herds 80%
Adults 35%, calves 80%
Dairy herds 55%
Adults 45%, calves 55%
Swine herds 86%
Adults 9%, weanlings 40%
Epidemiology
Prevalence
• Poultry
– Common wherever birds are raised commercially i.e.
disease of confinement
– 27% reported in broilers
Pathogenesis
• Intestinal cryptosporidiosis
• Enterocytes of the distal small
intestine-ileum
• C. parvum - villous atrophy,
villous fusion, crypt hyperplasia
& enterocyte sloughing
– Increased epithelial turnover
– Immature population of absorptive
cells
– Malabsorptive diarrhea
Pathogenesis
• Intestinal cryptosporidiosis
• C. baileyi infects the cloaca & bursa of
Fabricius in chickens & turkeys
• C. meleagridis intestinal infections
Pathogenesis
• Abomasal cryptosporidiosis
• C. andersoni
– Infects gastric peptic
glands
– Causes dilation of gland &
may impact performance
Pathogenesis
• Respiratory Cryptosporidiosis
• C. baileyi
– Inhalation or aspiration of
oocysts
– Impairs mucociliary elevator in
trachea & bronchi
– Few to no cilia found in heavy
infections
– Accumulation of mucus &
sloughed epithelial cells
– Results in air sacculitis &
pneumonia
Clinical signs
• Intestinal cryptosporidiosis
• Diarrhea
– Typically pasty-yellow in calves,
occasionally with blood or mucus
– Mild & intermittent or severe
profuse & watery
– May last up to two weeks
– General signs of enteritis &
dehydration
– Anorexia, abdominal cramping...
– Low mortality unless other
pathogens or stress factors (severe
cold & poor management) are
involved
Clinical signs
• Respiratory cryptosporidiosis
• Sneezing, coughing & other signs of respiratory distress
Diagnosis
• Histopathology
– Various stages in sections of ileum as round "blebs" on the
microvilli border
• Parasitophorous vacuoles
Diagnosis
• Fecal exam
• Sugar-centrifugal fecal flotation
– C. parvum oocysts
• Round & very small 4-6 um
– C. andersoni oocysts
• Slightly larger 6-8 um
– Both float just under the cover slip
– Difficult to see, requires experience
– Confused with the abundant yeast
– Oocysts may take on a pink
refractile appearance
Diagnosis
• Fecal exam
• Staining
– Acid fast stain of fixed smears
• Oocysts stain red, yeast stain
green
– Methylene blue & iodine used
on wet mounts
– Immunofluorescence antibody
stain
• Specific & sensitive
• Limited to diagnostic &
research labs
Treatment & Control
• No treatment currently available
– Nothing licensed
• Halofuginone &
azithromycin some efficacy
– Necessary?
• Sanitation & good management
– Reduce exposure to oocysts
• Supportive care
– Fluids, electrolytes & reduce
stress
Treatment & Control
• Adequate nutrition
– Important, administer in small
volumes so as not to overload the
gut
– Absorptive capacity is reduced
during infection
• Adequate colostrum
– Calves, lambs...
• Can be a chronic disease of the
immunocompromised & can be life
threatening
– AIDS patients &
immunosuppressive therapy
Protozoan Parasites:
Heteroxenous Coccidia - Part 1 & 2