Transcript Blood and Tissue Protozoa of Dogs and Cats

Blood Parasites of Dogs and
Cats
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
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
A three week old puppy
presented with anemia, icterus
after several littermates died
• Often concurrent with Ehrlichia canis
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
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
RBC’s.
• Organisms were found in <1% RBC
at ‘feathered tip’ of thin smears of
capillary blood. Giemsa stain is best
• Coomb’s test is +
• Serology: IFA of > 1:40 is diagnostic
of current or previous clinical disease
Ehrlichia canis
Ehrlichia canis is the cause of classical ehrlichiosis in dogs.
This Ehrlichia targets MONOCYTES
Ehrlichia canis infection in dogs is divided into 3
clinicopathologic stages:
acute phase of disease:
fever, anorexia, lethargy
lymphadenopathy
thrombocytopenia
This phase begins 1-3 weeks after exposure.
Most dogs recover at this point, but others progress to the
subacute and chronic phases
Ehrlichia canis cont:
subacute phase of disease:
hypergammaglobulinemia (polyclonal or sometimes
monoclonal gammopathy), thrombocytopenia and anemia
usually subclinical, but can last months to years
chronic phase:
lethargy, weight loss
PANCYTOPENIA, BONE MARROW SUPPRESSION
AND HEMORRHAGE
Heartworm Disease
Heartworm disease or dirofilariasis is a serious and potentially
fatal disease. It is caused by a blood-borne parasite known as
Dirofilaria immitis.
Adult heartworms are found in the heart and adjacent large blood
vessels of infected dogs. Rarely, worms may be found in other
parts of the circulatory system. The female worm is 6 - 14" long
(15 - 36cm) and 1/8" wide (5mm). The male is about half the size
of the female. One dog may have as many as 300 worms present
when diagnosed.
Heartworm Disease Lifecycle
Transmission
Since transmission requires the mosquito as an intermediate host,
the disease is not spread directly from dog to dog. Spread of the
disease therefore coincides with mosquito season, which can last
year-round in many parts of the United States. The number of dogs
infected and the length of the mosquito season are directly
correlated with the incidence of heartworm disease in any given
area.
The mosquito usually bites the dog where the hair coat is thinnest.
However, having long hair certainly does not prevent a dog from
getting heartworms.
Heartworm Disease in Cats
Heartworm disease in the cat may involve some or all of the following:
Pulmonary arterial, bronchial, and alveolar disease—Heartworm Associated
Respiratory Disease (HARD)—is associated with the death of developing juvenile
worms. Cats may present with cough, dyspnea, and/or wheezing.
Death of adult heartworms (if present) can potentiate HARD signs. Sudden death
occurs in approximately 10 to 20% of diagnosed cases. Pathogenesis is unclear, but a
condition (similar to acute respiratory distress syndrome [ARDS]) caused by the release
of antigenic moieties from injured or dying adult worms is suspected.
Vomiting unrelated to eating may be present.
Pulmonary thromboemboli (fragments from dead adult worms) may cause acute
vascular and interstitial inflammatory events that lead to dyspnea and death.
Hematological abnormalities may include anemia, hyperglobulinemia, basophilia, and
eosinophilia.
Neurological signs may indicate aberrant migration of the worm to the brain, eye, or
spinal cord.
Lifecycle in Cats
Mycoplasma hemofelis
(formerly Haemobartonella felis) is an epicellular bacterial
parasite of feline red cells that can cause hemolytic anemia. In
blood smears stained with polychrome stains, the organisms are
recognized as small blue cocci, rings, or rods on the edges or
across the faces of red cells. Stain precipitate is often mistaken
for organisms, resulting in unnecessary tetracycline
administration.
Mycoplasma hemofelis cont:
The hemolytic anemia caused by M. haemofelis is called feline
infectious anemia (FIA) and is usually regenerative in nature
(unless underlying disease suppresses the regenerative
response, e.g. Feline Leukemia Virus infection). Therefore, a
non-regenerative anemia in a cat with H. felis should not be
attributed only to M. haemofelis infection and the cat should
be further evaluated for another disease process
Cytauxzoon felis
• Causes a rapidly fatal disease in cats after <7
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 Wright’s stained
RBC, bone marrow or impression smears.
• Rx: Saved 6 of 500 cats by supportive care, parvaquone, 10-30mg/kg SID, 3d
QUESTIONS?
15