Blood and Tissue Protozoa of Dogs and Cats

1. Blood and Tissue Protozoa of Dogs and Cats

2. 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

3. 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

4. Clinical signs Acute Disease: Fever, anemia, icterus, splenomegaly, hemoglobinuria, azotemia, acidosis, low number 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 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.

5. Diagnosis ofBabesia • 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

6. 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 > 1:40; Bitches of affected litters had titers >1:1000 Typical greyhound kennel management

7. 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.

8. 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.

9. 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 (<2-years-old). Signs are referable to 3 phases: 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.

10. 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

11. 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.

12. 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

13. 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

14. 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

15. Hepatozoon canis • Hepatozoon occurs sporadically in dogs, usually < 6 months old in TX, LA, OK • 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: Imidocarb+Tetracycline?, Diminazene?, Primaquine? may be tried