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Blood and Tissue Protozoa
of Dogs and Cats
Babesia CanisTrypanosoma cruzi
Leishmania
L. donovani
L. chagasi
L. tropica Cytauxzoon felis
Hepatozoon canis
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Babesia canis
Endemic in southern Florida and sporadic elsewhere, especiallyin the southern states
Large, pleomorphic organisms in RBC are typical
Classic paired pyriform bodies of other Babesia species are rarelyseen in B. canis
B. gibsoni is rare, but
increasingly seen in the
USA and is found in dogs fromAsian enzootic areas
Small, singular annular bodies in
RBC are typical
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Babesia canis
Major strain differences in pathogenicity
Vector of transmission is the brown dog
tick, Rhipicephalus sanguineus
May be transmitted transovarially ortransstadially
Incubation period 10 days-3 weeks
Transmission possible by ticks, transplacentally orby blood transfusion
Pups, young dogs are more susceptible than adults,
especially kennels
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Clinical Signs
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 of Babesia
Acute Disease:
Fever, anemia, icterus, splenomegaly, hemoglobinuria, azotemia, acidosis
Low numbers of organisms (< 1% or RBC have 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 rarely seen 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 puppy that died RBC with organisms become
sticky and are taken out of
circulation.
Note multiple parasites in someRBCs.
Organisms were found in 1:40 is diagnostic of
current or previous clinical disease
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Kennel History:BabesiaOutbreak
Two affected litters were born in this kennelhousing 23 adult dogs
Numerous brown dog ticks (R sanguineus) ofall stages (larvae, nymphs, adults) were found
Serologic testing by IFA of dogs in
outside runs revealed that about
had titers > 1:40
Bitches of affected litters had titers
>1:1000
Typical
greyhoundkennel
management
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Treatment and Control
Imidocarb diproprionate (Imazole ) is the treatment of choice
Also effective against Ehrlichia canis, often found concurrently with Babesiaand
also transmitted by R sanguineus
Diminazene aceturate (Ganaseg , Berenil ) is also effective
Phenamidine isothionate and 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 plus once per month kennel spray recommended
Insecticide resistance common in kennels sprayed frequently
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 majorhuman disease in South America.
Reduviid bugs reside in cracks and
crevices,
especially in mud brick houses
They emerge and feed on mucous
membranes at night
Circulating trypomastigotes in blood
meal develop in reduviid vectors
(kissing bug, assassin bugs)
Infect by stercorarian transmission,
(organisms deposited by defecation
on bite wound); dog ingestion of bug
Transfusions; Transplacental possible
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Distribution of T. cruziin the USA
In the USA, Chagas disease
is a sylvatic disease circulating
in opossums, raccoons, otherwild mammalian hosts
Can incidentally infect and
cause clinical disease in ruraldogs, esp young< two years
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3 clinical phases of T. cruzi
Acute Phase: circulating organisms present
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
Intermediate Phase:
Asymptomatic with no parasitemia for years
Chronic Phase: dilatational cardiomyopathy in dogs and human
death due to congestive heart failure or arrhythmias
Megacolon may occur in man (Charles Darwin reputedly died of this!)
Chronic disease pathogenesis is obscure
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T. cruziamastigotes 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 are moreaccurate, 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: feed reduviid bug on host, hold 20-40 days, examine Culture by LIT medium or cell culture inoculation with blood
CDC offers IFA diagnosis of veterinary cases; PUBLIC HEALTH -Human
infection via mucous membrane exposure; Lab infections; a BL-2 pathogen
Rx: Acute-benznidazole nifurtimox Su ortive care Vector Control-S ra s
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Leishmania spp. = Leishmaniasis
A major veterinary and public health disease in LatinAmerica, Africa, Asia and the Mediterranean basin where20-40% of dogs and 1-2% of children are infected
Dogs are main reservoir in the old world; wildlife S Amer
A small focus occurs in the Southwest USA;
Especially in 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.
Amastigotes of
Leishmania spp. in
macrophage of dog
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Leishmania amastigotes
Amastigotes are round organisms with a nucleusand diagnostic dark cylindrical kinetoplast
Circulate in the blood intracellularly in monocytes
In the visceral form, amastigotes nests occur in
phagocytes in major vascular organs rich in RE
cells
3-7 month incubation period after a transient
cutaneous lesion (L. donovani, L. infantum)
Rodents are common reservoirs
In cutaneous forms (L. tropicacomplex), lesions confined to skin
Dogs: 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 (after wet season) 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 < 7
days of 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-
107o F febrile period
Dx: via organism in Giemsa or Wrights stained RBC, bone marrow or
impression smears
Rx: Saved 6/500 cats by supportive care, parvaquone, 10-30mg/kg SID, 3d
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Hepatozoon canis Occurs sporadically in dogs, usually < six months
old in TX, LA, OK Infection is by ingestionof R. sanquineus, in whichsporogony occurs
Signs include intermittent fever, stiffness ofmuscles and periosteal inflammation due to
release of merozoites from tissue schizonts Periosteal bone proliferation in proximal long bones visible by radiograph isdiagnostic
In the dog, schizogony occurs in phagocytic cells of the RE cells of major
organs, myocardium and skeletal muscles
They produce 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: Acute: Sulfadiazine+Clindamycin+ Pyrimethimine; Chronic: Decoquinate