Blood and Tissue Protozoa of Dogs and Cats

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Blood and Tissue Protozoa of Dogs and Cats

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Babesia canis

• B. canis is endemic in southern Florida, sporadic
  elsewhere, especially in the southern states
  Large, pleomorphic organisms in RBC are typical
  classic paired pyriform bodies (below) are rare
  in this species.
• B. gibsoni is rarely seen in the USA and is
  found in dogs from Asian enzootic areas small,
  singular annular bodies in RBC are typical

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Babesia canis

• Pups, young dogs are more susceptible than
  adults, especially kennels
• Major strain differences in pathogenicity
• Rhipicephalus sanguineus transmits
  transovarially, transstadially
• Incubation period 10 days-3 weeks transmission
  possible by ticks, transplacentally or by
  transfusion
• Often concurrent with Ehrlichia canis

A three week old puppy presented with anemia,
icterus after several littermates died in a
greyhound kennel

• Signs and pathogenesis are referable to
  regenerative hemolytic anemia. In clinical cases,
  aggregates of parasitized RBC-fibrin ? sludging
  of capillary beds ? tissue anoxia, vascular
  damage, especially brain, heart, kidneys,
  intestines? acidosis, DIC ? shock and death

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Clinical signs
Acute Disease Fever, anemia, icterus,
splenomegaly, hemoglobinuria, azotemia, acidosis,
low number of organisms (parasites) are found, even in the acute phase.
Parasitemia is transient at 3-4 days, reappears
at 10 days and peaks at 3 weeks. Chronic
Disease Immunity (premunition) leads to a
balance of the parasite and host immunity
organisms are rare in blood in chronic
infections stress may lead to recrudescence and
sporadic episodes of hemolytic crisis (eg.
Pregnancy may activate infection ? Transplacental
transmission to pups). Adult dogs and previously
affected dogs are typically asymptomatic, chronic
carriers.
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Diagnosis of Babesia

• Spleen, liver impression smears of a littermate
  that had died. RBC with organisms become sticky
  and are taken out of circulation. Note multiple
  parasites in some RBCs.

• Organisms were found in tip of thin smears of capillary blood. Giemsa
  stain is best
• Coombs test is
• Serology IFA of 140 is diagnostic of
  current or previous clinical disease

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Kennel History Babesia outbreak

• The 2 affected litters were born in this kennel
  housing 23 adult dogs Numerous brown dog ticks
  (R sanguineus) of all stages (larvae, nymphs,
  adults) were found

• Serologic testing by IFA of dogs in outside runs
  revealed about ½ had titers 140 Bitches of
  affected litters had titers 11000

Typical greyhound kennel management
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Treatment and Control

• Imidocarb diproprionate (Imazole) is treatment of
  choice It is also effective against Ehrlichia
  canis, which is often found concurrently with
  Babesia and is also transmitted by R sanguineus.
  Diminazene aceturate (Ganaseg, Berenil) are also
  effective Phenamidine isothionate, trypan blue
  are older, less effective drugs. No accepted
  effective treatment exists for B gibsoni.
• Tick control is essential to break the two-month
  tick life cycle. Weekly dip of all dogs, once
  per month kennel spray insecticide resistance
  common
• Dip and quarantine all incoming dogs for 3
  weeks eliminate serologically positive carriers.
  
• A vaccine is available in Europe, elsewhere.

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Trypanosoma cruzi

• T. cruzi causes Chagas disease, a major human
  disease in South America.
• Reduviid bugs reside in cracks, crevices,
  especially in mud brick houses, emerge and feed
  on mucous membranes at night

• Circulating trypomastigotes in blood meal develop
  in reduviid vectors (kissing bug, assassin bugs)
  and infect host by stercorarian transmission,
  by organisms deposited by defecation on bite
  wound. Tranfusions can transmit.

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Distribution of T. cruzi in the USA

• In the USA, Chagas disease is a sylvatic disease
  circulating in raccoons,other wild mammallian
  hosts and can incidentally infect and cause
  clinical disease in young, rural dogs
  (The acute phase, with circulating organisms,
  coincides with

invasion, multiplication and rupture of cells,
especially in cardiac muscles. Acute
myocarditis, with ventricular tachycardia, right
heart failure, ascites, hepatomegaly, anemia, and
sudden death may occur, /- neurological signs
the intermediate phase, asymptomatic with no
parasitemia for years and the Chronic phase, with
dilatational cardiomyopathy (in dogs and human)
and death due to congestive heart failure or
arrhythmias Megacolon may occur in man (Charles
Darwin died of this). Chronic disease
pathogenesis is obscure.
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T cruzi amastigotes in cardiac tissues

• Circulating trypomastigotes occur concurrently
  in hosts with amastigotes, especially in the
  cardiac musculature
• Low numbers of trypomastigotes may be found in
  thin blood smears Giemsa stained thick smears
  more accurate, especially if examine buffy coat
  of a microhematocrit tube

• Organisms seen 3-6 day after infection, peak at
  2-3 weeks in acute phase
• Xenodiagnosis by feeding reduviid bug on host,
  hold 20-40 days, examine
• Culture possible by LIT medium, cell culture
  inoculation with blood
• Serology is offered by CDC for diagnosis of
  veterinary cases
• Rx, Control No effective drug supportive
  care spray houses for vectors

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Leishmaniasis

• A major veterinary and public health disease in
  Latin America, Africa, Asia and the Mediteranean
  basin where 20-40 of dogs and 1-2 of children
  nare infected Dogs are the main reservoir in the
  old world
• A small focus occurs in the Southwest USA
  military family dogs from endemic zones
• Recent recognition of significant disease in
  Foxhounds in the Eastern USA epidemiology is
  obscure, possibly transmitted via dog bites
• Visceral leishmaniasis typically causes
  cutaneous lesions in dogs, with alopecia,
  depigmentation, hyperkeratosis, in addition to
  lymphadenopathy, deep visceral organ involvements.

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Leishmania amastigotes, impression smear

• Amastigotes, round organisms with a nucleus and
  diagnostic dark cylindrical kinetoplast,
  circulate in the blood intracellular in monocytes
• In the visceral form, amastigotes nests occur
  in phagocytes in major vascular organs rich in RE
  cells there is a 3-7 month incubation period
  after a transient cutaneous lesion (L. donovani,
  L. infantum)
• In cutaneous forms (L. tropica complex) lesions
  confined to skin, rodents are common reservoirs

• Finding amastigotes by biopsy of skin, lymph
  nodes, spleen or liver is diagnositic

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Sandfly intermediate hosts

• Phlebotomus spp (sandflies) are intermediate
  hosts. Infection by ingestion of organism in
  monocytes.
• Sandflies are found in protected, internally
  humid foci such as rodent burrows, mainly in arid
  climates. Transmission is seasonal and tends to
  be focal where favorable sandfly environments
  occur

• TREATMENT of leishmaniasis Megumine
  antimoniate, Na stibogluconate SID for 3 weeks

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Cytauxzoon felis

• Causes a rapidly fatal disease in cats after day illness. Signs referable to occlusion of
  vasculature by schizonts in MN phagocyte lining
  of all organs, especially lungs
• Sporadic in rural cats in South, Southcentral
  USA Tick vector (Dermacentor, Ixodes?) with a
  bobcat reservoir suspected.
• There is both a tissue and RBC phase of the life
  cycle. Merozoites parasitize 1-4 of circulatiing
  RBC 1-3 days prior to death. Signs are
  depression, anorhexia, dyspnea, icterus, anemia,
  terminal 103-107 F febrile period. Dx via
  organism in Giemsa or Wrights stained RBC, bone
  marrow or impression smears.

• Rx Saved 6 of 500 cats by supportive care,
  parvaquone, 10-30mg/kg SID, 3d

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Hepatozoon canis

• Hepatozoon occurs sporadically in dogs, usually
  
• Infection is by ingestion of R. sanquineus in
  which sporogony occurs

• Intermittent fever, stiffness of muscles and
  periosteal inflammation due to release of
  merozoites from tissue schizonts Periosteal bone
  proliferation in proximal long bones visible by
  radiography? Diagnostic

• In the dog, schizogony occurs in phagocytic
  cells of the RE cells of major organs, myocardium
  and skeletal muscles, producing merozoites which
  produce gametocytes that circulate in the blood
  in neutrophils, monocytes for tick vector. Dx
  Find gametocytes in blood smears or schizont by
  muscle biopsy. Rx
  ImidocarbTetracycline?, Diminazene?, Primaquine?
  may be tried