Pa Blood Tissue Protozoa Dogs Cats

Blood and Tissue Protozoa of Dogs and Cats • Babesia Canis

•Trypanosoma cruzi • Leishmania • L. donovani • L. chagasi • L. tropica • Cytauxzoon felis • Hepatozoon canis

Babesia canis • Endemic in southern Florida and sporadic elsewhere, especially in the southern states • Large, pleomorphic organisms in RBC are typical • Classic paired pyriform bodies of other Babesia species are rarely seen in B. canis • B. gibsoni is rare, but increasingly seen in the USA and is found in dogs from Asian enzootic areas • Small, singular annular bodies in RBC are typical

Babesia canis • Major strain differences in pathogenicity • Vector of transmission is the brown dog tick, Rhipicephalus sanguineus • May be transmitted transovarially or transstadially • Incubation period 10 days-3 weeks • Transmission possible by ticks, transplacentally or by blood transfusion • Pups, young dogs are more susceptible than adults, especially kennels

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

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.

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 some RBC’s. • Organisms were found in <1% RBC at ‘feathered tip’ of thin smears of capillary blood. • Giemsa stain is best to use • Coomb’s test is positive • Serology: IFA of > 1:40 is diagnostic of current or previous clinical disease

Kennel History: Babesia Outbreak • Two 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

Typical greyhound kennel management

• Serologic testing by IFA of dogs in outside runs revealed that about
had titers > 1:40 • Bitches of affected litters had titers >1:1000

Treatment and Control • Imidocarb diproprionate (Imazole
) is the treatment of choice • Also effective against Ehrlichia canis, often found concurrently with Babesia and 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

Trypanosoma cruzi •T. cruzi causes Chagas disease, a major human 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

Distribution of T. cruzi in the USA

• In the USA, Chagas disease is a sylvatic disease circulating in opossums, raccoons, other wild mammalian hosts • Can incidentally infect and cause clinical disease in rural dogs, esp young< two years

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

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 are 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: 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; Supportive care; Vector Control-Sprays

Leishmania spp. = Leishmaniasis • A major veterinary and public health disease in Latin America, Africa, Asia and the Mediterranean basin where 20-40% 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 Amastigotes of Leishmania spp. in macrophage of dog

• 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.

Leishmania amastigotes • Amastigotes are round organisms with a nucleus and 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. tropica complex), lesions confined to skin • Dogs: Finding amastigotes by biopsy of skin, lymph nodes, spleen or liver is diagnositic

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

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 • There both a tissue and RBC phase of the life cycle bobcatisreservoir suspected. • Merozoites parasitize 1-4% of circulatiing RBC 1-3 days prior to death • Signs are depression, anorhexia, dyspnea, icterus, anemia, terminal 103107o F febrile period • Dx: via organism in Giemsa or Wright’s stained RBC, bone marrow or impression smears • Rx: Saved 6/500 cats by supportive care, parvaquone, 10-30mg/kg SID, 3d

Hepatozoon canis • Occurs sporadically in dogs, usually < six months old in TX, LA, OK • Infection is by ingestion of R. sanquineus, in which sporogony occurs • Signs include 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 radiograph is diagnostic • 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