Parasites of circulatory system

Question 1

Dirofilaria immitis = parasites of the _____

Answer 1

pulmonary arteries

Question 2

Purpose/function of Wolbachia of Dirofilaria immitis

Answer 2

• symbiotic bacteria that is required for survival and reproduction of the nematode.
• release associated w/ increase in inflammatory cytokines + decr. in host immune response

Question 3

Caval syndrome

Answer 3

Most severe manifestation of HW dz
- >40 worms migrate into RV, RA and Caudal Vena Cava –> interfere w/ valv. function and/or bloodflow
- acute clincial syndrome = DIC
- if worms not surgergically removed, fatal outome

Question 4

When worms die during tx, what is a consequence and why dogs must be kept calm/exercise limited?

Answer 4

Thromboembolism
- dead worms worse vascular damage and enhance coagulation

Question 5

What is the only state where HW is NOT endemic?

Answer 5

Alaska

Question 6

How is Dirofilaria immits diagnosed?

Answer 6

Detecting microfilaria via direct smear or Knott’s test (a concentration technique- best per AHS)

stained blood smear

Knott’s test involves using a centrifuge (a machine that spins the sample very quickly in a small circle) to concentrate the microfilariae

Question 7

Snap antigen test for Dirofilaria immitis detects antigen from where? What can cause a false negative?

Answer 7

The uterus/adult female repro tract. False negative = male-only infection, low female infection, a PPP infection, production of antigen-antibody complexes in dogs

Question 8

False negatives for Knott’s Test

Answer 8

Question 9

How do macrocylic lactones (avermectins, milbemycins) prevent HW dz?

Answer 9

kill immature worm (prevent from developing into adult)

Question 10

What life cycle stage are macrocyclic lactones approved for?

Answer 10

1 dose will kill L3 and L4 up to 6-8 weeks post infection

most L3 mature into L4 is SC tissue in 1-3 days -> L4 migrate thru tissue and mature into sexually immature/adolescent adults b/w 50-70 days -> sexually immature worms migrate to heart and lungs -> worms develop into sexually mature in pulmonary artery -> microfilariae appear in blood b/w 6-7 months PI = stage where MF are killed

Question 11

When is a dog considered cleared of HW infection with adulticide tx?

Answer 11

after 2 consecutive NAD (no antigen detected), 6 months apart

Question 12

What is the most common clinical syndrome observed in cats infected with HW?

Answer 12

Heartworm Associated Respiratory Disease (HARD)
- occlusive medial hypertrophy of small pulmonary arterioles –> disease in cats is due to MIGRATION of the larvae

may be misdiagnosed as asthma or allergic bronchitis

Question 13

How is feline HW diagnosed?

Answer 13

there is no single test that will detect all HW cases.

only confirms that there are adult nematodes in the pulmonary arteries, does not verify that clincial signs are cuased by larval migrating tin the respiratory tract

Question 14

HW disease: interpret a positive antigen result in cats

Answer 14

only confirms that there are adult nematodes in the pulmonary arteries, does not verify that clincial signs are caused by larvae migrating around in the respiratory tract!

Question 15

What transmits Piroplasms

Answer 15

Hard (Ixodid) ticks

Piroplasms = blood parasite

Question 16

Babesia spp. pathogenesis and clinical signs

Answer 16

Erythrocyte lysis, asspocated with parasite release –> fever, hemoglobinuria, anemia, icterus, splenomegaly

Babesia = type of piroplasm

Question 17

What causes Texas Cattle fever

Answer 17

Babesia sp. transmitted to cattle via Rhipicephalus (Brown dog) ticks
- One-host ticks (infest animal as larva, remain on same animal thru adult stage)
- a serious livestokc dz -> we eliminated the tick

Question 18

How is Canine Babesiosis transmitted (2)

Answer 18

1. Rhipicephalus sanguineus (tick) transmits the organisms after 24-48 hours of feeding
2. Direct transmission (iatrogenic via needles, dog-to-go via FIGHTING [esp. B. gibsoni])

Question 19

What organism and what tick are involved in Feline Piroplasmosis

Answer 19

Cytauxzoon felis transmitted by Amblyomma americanum (Lone Star Tick), affecting bobcats and cats

Question 20

Pathogenesis of Cytauxzoon felis

Answer 20

sporozoites in cat enter endothelial møs and multiply (schizogony) –> disease from occlusion of small vessels in lungs, spleen, liver and kidney, + RBC loss

acute fever, resp. signs, depression, icterus, lethargy, anorexia

Question 21

Bovine theileriosis

Answer 21

Theileria in cattle spread by longhorned Asian tick (Haemaphysalis longicornis) – Asia, Australia and NZ

Question 22

Trypanosoma cruzi
- type of organism
- species affected
- location

Answer 22

• flagellate, protozoan organism
• infects dogs and wild animals
• Cases mostly in Texas and Gulf Coast region

Question 23

Life cycle and pathogenesis of Trypanosoma cruzi

Answer 23

KEY: transmitted thru the FECES of the kissing bugs –> enters host bloodstream & multiply in cardiac cells

Question 24

Clinical signs of Trypanosoma cruzi

Answer 24

• Peracute death from acute myocarditis;
• Chronic: heart failure (months-year; more common)