Coccidia

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Coccidia of Small Animals
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Isospora (Cystisospora), other coccidiaDog
Cat

• I. canis 35-45u
• I. ohioensis 20-30u
• I burrowsi 17-22u
• I. neorivolta 20-30u
• I. bigemina 10-12u
• Neospora caninum 10-12u
• Sarcocystis spp 10-12u
• Cryptosporidium 4-6u
• (Hammondia heydorni)

• I. felis 35-45u
• I. rivolta 20-30u
• Hammondia
• hammondi 10-12u
• Besnoitia 10-12u
• Sarcocystis 10-12u
• Toxoplasma 10-12u
• Cryptosporidium 4-6u
• Assume Toxoplasma unless know otherwise

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Comparison of (clockwise) of Isospora felis, I.
rivolta, Toxoplasma and Sarcocystis of cats size
ranges similar for dog coccidia
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I. felis and I. rivolta in comparison to
Ancylostoma
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• All Isospora of dogs and cats
• 2 sporocysts with 4 sporozoites
• Intestinal cycle with monozoic cysts in tissues
  (paratenic hosts have only monozoic cysts
• One week prepatent period
• High host specificity

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Banana-shaped sporozoite from excysted sporulated
oocyst. These invade intestinal epithelial cells
to initiate schizogony or invade other tissues
(eg. Lymph nodes) as monozoic cysts
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• Developing schizont (Meront)in intestinal
  epithelium cell
• SchizogonyMerogony, asexual reproduction
• 1-4 schizogony cycles ? merozoites

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• Gametogony (sexual reproduction)
• Macrogametocyte fertilized by microgamete ?
  zygote ? Oocyst

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Unsporulated oocysts are shed in feces
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Clinical signs Treatment

• Most exposed early in life ? Immune
• Massive exposure ? bloody diarrhea, enteritis
• Especially puppy mills, pet shops
• Main factors number of oocysts exposure and
  immune state
• Often follows immunosuppression (eg shipping
  stress, distemper)

• Sulfa drugs (eg Albon)
• Furozolidone
• Amprolium prophylaxis or treatment prior/after
  weaning/shipping
• Supportive Rx until immunity builds
• Prepatent period one week
• Self-limiting maximum oocysts shed for 1 week,
  greatly reduce or cease in 2 week patent period
  unless immunosuppressed

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Toxoplasma gondii
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Sporulated oocysts of Toxoplasma gondii

• Oocysts shed by cats only (and other felidae)
• Shed 10 million oocysts beginning 5-14 days
  after infection
• Self-limiting after patent period of 2-3 weeks
• Cats do not shed on second exposure, thus safe
  (unless immunosuppressed)
• Sporulate to infective form in 2 days -- change
  cat litter 1x/day gardeners beware oocysts
  survive 1 year in moist, cool Cat is pivotal
  factor as source of herbivore infections

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• Sources of Toxoplasma infection in Cats
• Carnivorism (via bradyzoites, tachyzoites) most
  efficient route high of cats shed large number
  of oocysts
• Oocysts - 50 of cats shed small number of
  oocysts
• Congenital Clinical signs seen in offspring,
  especially if 1st trimester exposure

• Cats develop both 1) the enteroepithelial phase
  of schizogony, gametogony in gut with oocyst
  shedding, and 2) the extraintestinal tissue phase
  of other hosts. Toxoplasma is an obligate
  intracellular, pantropic organism that can infect
  any warm-blooded vertebrate (including birds). In
  the extraintestinal phase, sporozoites,
  bradyzoites or tachyzoites invade lymph nodes,
  disseminate via lymph or blood to liver, lung
  then other tissues.

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• Rapid, proliferative schizogony (tachyzoites)
  occurs /- clinical disease in intracellular
  pseudocysts until contained by immunity in 7-10
  days. The organism then persists long-term
  asymptomatically as bradyzoites especially in
  reticuloendothelial system cells of the liver,
  lung, brain, eye, lymph nodes. When only
  partially contained, periodic recrudescence of
  multiplication, necrosis of tissues occurs,
  producing chronic disease with signs depending
  on tissue location of organisms and lesions.
• Congenital infections occur by invasive,
  proliferative tachyzoites in the potentially
  acute phase of the disease.

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Toxoplasma is found in highest prevalence in
moist environments in the USA and globally.
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The cat is the key epidemiological factor in
infection of herbivores. Surveys reveal about 1
of pound cats are shedding Toxoplasma oocysts at
any one time. Sheep may abort or produce weak
lambs if exposed during pregancy, but only once,
then are immune.
Placentitis
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• Carnivorism, not oocyst exposure, is the most
  important source of infection of humans Beeflt
  chicken lt horse lt lamb/goat lt pork
• Cattle are relatively resistant hosts and
  organisms are difficult to isolate from tissues,
  does not persist more than a few months Filet
  mignon is OK?

• Chicken is usually frozen or well cooked
  Horsemeat not eaten in US
• Lamb/goats 5 of market lambs infected can
  pass in goat milk
• Pork 1/3 infected in US surveys 6 of
  hamburger contaminated by added pork, butcher
  equipment Rare burgers have risk

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• Prevention in Food Sources
• Heat to over 70 C
• Experimental irradiation, specialty market -
  30Krad for pork kills organism and many bacteria
• Meal preparation Wash hands after handle raw
  meat one cyst ? 100,000 bradyzoites
• Salting, curing kills
• Freezing with home freezer temperatures (-40F)
  kills but not reliable

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Public Health

• Surveys reveal 1/3 people have titers to
  Toxoplasma, increases with age Usually immune
  to new infection May recrudesce with fatal
  results if immunosuppression (eg AIDS patients)
• Humans usually develop asymptomatically or have
  flu-like symptoms in the acute phase Death
  possible but most recover completely some
  develop low-grade seething, recurrent chronic
  disease, especially eye, brain, liver, lung,
  lymphatic tissues. Location determines signs.
  Toxoplasma is thus often on differential
  diagnosis lists
• If infection of non-immune mother occurs in
  pregnancy, 20-50 of fetus will be infected, some
  will abort
• Most damage to fetus if infected in the first
  trimester ? Anencephaly, blindness, retardation,
  etc. Toxoplasma estimated to occur in 1 of 1000
  births, most are asymptomatic, some delay signs
  for years (eg. until puberty)
• Number of infective stages ingested, immune state
  are the crucial factors in infection course

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Diagnosis

• Oocysts in cats can be found by flotation
  procedures at 5-24 days post infection only
• Sheathers sugar (5 lb sucrose 1450 water
  29 g phenol) is best
• Do Double Flotation float 10 minutes,
  coverslip, let float to under coverslip 10
  minutes film is 100u, Toxoplasma only 10-12u
  Focus just under coverslip

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• Serology
• Reliable human, dog, other species
• Cats notorious for developing low, unreliable
  titers after 4-6 weeks
• Sabin-Feldman Dye test (oldest test)
• IFA Common use IgM early
• ELISA Detect IgM, IgG, Antigen
• IHA, CF Late IgG, not as sensitive
• Do paired sera 2-3 weeks apart 4x rise in
  titer is diagnostic gt1256 considered positive
  for active infection, especially cats 11024 is
  the cut-off by many for clinical disease
• There are many different strains for Toxoplasma
  (and other protozoan diseases)

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Animal inoculation

• Animal inoculation can be done using oocysts or
  tissue (pepsin digest wash) with oral,
  intraperitoneal or intracranial infection of
  mice, rats.
• Find organism in peritoneal fluid in 4-5 days,
  in tissues 4-6 weeks, by serology in 3 weeks

Peritoneal fluid
Impression smear
Brain section
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Treatment

• Sulfa drugs Sulfadiazine (60mg.kg.day)
  Pyrimethamine (0.5-1.0 mg/kg/day) yeast or
  folinic acid (for side effects), or long acting
  sulfa drugs (eg Tribrissen, Di-Trem)
• Clindamycin is drug of choice
  

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• Classic predator-prey life cycle, numerous
  species
• High host specificity
• Gametogony sporogony in predator, Schizogony
  tissue phase in prey
• Acute disease possible in proliferative
  schizogony phase (counterpart of tachyzoites) in
  reticuloendothelial tissues
• Skeletal and cardiac muscle tissue stage is
  quiescent (counterpart of bradysoites)
• May shed high numbers for extended periods (eg
  60 days) little gut pathogenicity No immunity
  to re-infection develops in predators
• Human Isospora now known to be S. bovihominis
  or S. porcihominis

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Hammondia

• Indistinquishable from Toxoplasma (10-12u)
• Non-pathogenic in cats which have intestinal
  gametogony phase only Schizongony in muscle
  tissue of rodent hosts Sporogony in the
  environment

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Besnoitia

• Slightly larger than Toxoplasma (12-17u)
• Asymptomatic gametogony in cat, sporogony in
  environment, schizogony in subcutaneous tissues
  of rodent, herbivores, etc
• Differential diagnosis importance only

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Cryptosporidium

• Occurs in dogs and cats, but low prevalence
• Probably of minor clinical or public health
  importance
• Differentiate from yeast, which are not acid
  fast and are variable in size

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Neospora caninum

• Newly described in dog (1988)previously
  confused with Toxoplasma
• Oocysts 10-12u in size are shed by dogs Source
  of infection for abortion in dairies, beef cattle
  
• Ultrastucture, immunohistochemistry different
  from Toxoplasma
• Clinical disease may result in dogs which is
  similar to Toxoplasmosis, but neurological and
  muscular abnormalities predominate with Neospora

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Pneumocystis carinii

• Organism of uncertain taxonomy (yeast vs
  sporozoan) that infects respiratory tissues of
  humans, dogs, other species, most subclinical ,
  lt10 dry non-productive cough
• If immunosuppress, proliferate in alveoli with
  clinical disease
• Diagnosis by transtracheal wash, biopsy or
  sputum sample ? ID organism By histopathology,
  does not stain with Hemotoxylin and Eosin must
  use special stains including Giemsa, Wrights,
  Gram stain or Silver stain (the latter is best)
• Treatment may be tried with sulfas (eg
  Tribrissen), pentamidine isothionoate