Parasitology lab notes


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Parasitology lab notes

  1. 1. Introduction to Blood Parasites Dirofillaria immitis & Dipetalonema reconditum
  2. 2. Dirofilaria immitis: Canine Heartworm <ul><li>Commonly known as canine heartworm but can infect cats & ferrets also </li></ul><ul><li>Dogs are definitive hosts </li></ul><ul><li>Adults normally reside in the right ventricle & pulmonary arteries ( occult infection : when infected with adults only!) </li></ul><ul><li>Offspring are called microfilariae </li></ul><ul><li>Many can wander – becoming aberrant – they get lost on the way to the heart & can be found in variety of extravascular sites including cystic spaces in subcutaneous sites, the brain, & anterior chamber of the eye </li></ul>
  3. 3. Dirofilaria immitis: Life Cycle <ul><li>Prepatent period= 5-6 months </li></ul><ul><li>Life cycle requires intermediate host – Mosquito. </li></ul><ul><li>Sexual reproduction – both males & females </li></ul><ul><li>Microfilariae are released into bloodstream, where ingested by feeding mosquito </li></ul><ul><li>Microfilariae grow & milt inside mosquito until reach infective 3 rd stage larvae </li></ul><ul><li>Once they become infective, they migrate to the mouth parts of the mosquito. When mosquito bites new host, microfilariae are injected into new host’s bloodstream. </li></ul><ul><li>They migrate & molt until they reach the heart </li></ul>
  4. 4. Dirofilaria immitis: Signs & Symptoms <ul><li>Can be asymptomatic </li></ul><ul><li>Coughing, weakness, lethargy, exercise intolerance, hypertension, liver & kidney failure, abdominal ascites, pulmonary edema & right sided congestive heart failure </li></ul><ul><li>Can be fatal!!!! </li></ul><ul><li>Caval syndrome: overload of worms in heart, right atrium & caudal vena cava. Needs surgical intervention or animal will quickly die </li></ul>
  5. 5. Dirofilaria immitis: Diagnosis <ul><li>Commercial snap test (ELISA) – needs to have females present! </li></ul><ul><li>Other serologic tests </li></ul><ul><li>Modified Knott’s test – milipore filtration, concentration techniques (blood samples are centrifuged &/or filtered to concentrate microfilariae) </li></ul><ul><li>Blood smear </li></ul><ul><li>X-rays – to check for right sided heart enlargement </li></ul>
  6. 6. Dirofilaria immitis: Prevention & Treatment <ul><li>Ivermectin (Heartguard), Milbemycin (Interceptor & Sentinel), Moxidectin (ProHeart) </li></ul><ul><li>Preventative drugs are HIGHLY effective. When administered properly will prevent over 99% of infections. </li></ul><ul><li>Preventatives are microfilaricides and will kill microfilariae that are present. Therefore testing is necessary before beginning preventatives </li></ul><ul><li>Treatment is difficult. </li></ul><ul><li>First, testing is done to determine how fit the animal is for treatment by doing bloodwork & x-rays. </li></ul><ul><li>Second step is administering adulticides like Immiticide. As adults die – they move with flow of blood toward lungs – can cause problems if allowed to exercise after adulticide treatment. </li></ul>
  7. 7. Dirofilaria immitis: Treatment (cont’d) <ul><li>Dog MUST be kept quiet (crated) for several weeks after treatment while body reabsorbs dead adults. </li></ul><ul><li>After adults are treated, dog is administered microfilaricide (usually ivermectin) to clear the blood of any microfilariae. </li></ul><ul><li>Final part of treatment is testing with ELISA to confirm all heartworms have been cleared from the body. </li></ul><ul><li>Treatment is VERY STRESSFUL. This is why it is so important to stress to clients that it is easier to prevent heartworm than to treat it! </li></ul>
  8. 8. Dipetalonema reconditum: Subcutaneous filarial worm <ul><li>Also produces microfilariae. </li></ul><ul><li>Often confused with Dirofilaria immitis </li></ul><ul><li>Nonpathogenic nematode resides in subcutaneous sites in dogs. </li></ul><ul><li>Intermediate host is FLEA!!! </li></ul><ul><li>Tests: modified Knott’s, milipore filtration, blood smear </li></ul><ul><li>Transmission: Infective flea bites, ingestion of fleas </li></ul>
  9. 9. Microfilariae in Blood Smears: Dirofilaria immitis vs. Dipetalonema reconditum <ul><li>Dirofilaria immitis </li></ul><ul><li>Large numbers </li></ul><ul><li>Undulates in one place </li></ul><ul><li>Tapered head </li></ul><ul><li>Straight tail </li></ul><ul><li>120-310mm – much larger!!! </li></ul><ul><li>Dipetalonema reconditum </li></ul><ul><li>Few in numbers </li></ul><ul><li>Moves across field </li></ul><ul><li>Blunted head </li></ul><ul><li>Button-hooked tail </li></ul><ul><li>9-32mm – smaller!!! </li></ul>