HW Dz (Dog) Flashcards
Life Cycle of HWs
Adult worms living in pulmonary vessels reproduce –> microfilaria –> circulate thru systemic circulation –> ingested by mosquito during blood meal from infected dog –> microfilaria develop to L3 in mosquito –> at L3, microfilaria are infective –> can now be transmitted to another animal when mosquito takes another blood meal –> basically get injected into systemic circulation of another animal –> travel to pulmonary vessels –> mature into adult worms that can reproduce
List some of the areas where HW Dz is know to exist
All 50 states Puerto Rico Guam US Virgin Islands Parts of Canada Mexico Australia South America
Name the 2 primary effects of adult HWs on the pulmonary vasculature
Villous Endarteritis
Pulmonary Thromboembolism
Describe villous endarteritis
- Inflammatory response within pulmonary vessels leads to proliferation of the mucosal lining of the blood vessels
- Mucosal lining goes from smooth to almost villi texture which changes blood flow thru the vessel
Describe Pulmonary Thromboembolism (PTE)
- Villous endarteritis makes blood flow turbulent, leading to activation of coagulation cascade that results in formation of small blood clots within the blood vessels that can travel into the pulmonary vasculature
- Clots lodge within small vessels and cut off blood flow resulting in infarcted region of the lungs
Explain how HW Dz may lead to right-sided CHF (start with the 2 things that change in the body when infected with HWs)
- Villous endarteritis & PTE decrease blood flow and increase pressure in pulmonary vasculature
- Increased pressure –> pulmonary hypertension
- The heart works against this pressure resulting in right ventricle hypertrophy (enlargement)
- Right ventricle muscle weakens and fails to pump blood adequately
When does caval syndrome develop?
Develops w/ excessive worm burden where large # of worms spill out of pulmonary artery into right atrium and cranial/caudal vena cava
What do HWs in the vena cava do to the body?
Worms in vena cava severely disrupt systemic circulation b/c it significantly decreases blood flow into the heart and increases pressure in the venous system
Clinical Signs of HW Dz, Dz caused by HW Dz (think of how blood gets disrupted and what parts of HW Dz can cause that)
- Coughing +/- blood
- Pulmonary Thromboembolism
- Pulmonary Hypertension
- Ascites & Hepatic Congestion
- Acute Respiratory Distress
- Dyspnea
- Caval Syndrome
Pathophysiology of coughing in HW Dz
vascular inflammatory reaction to infection with worms (villous endarteritis) irritates the respiratory system
Pathophysiology of pulmonary thromboembolism in HW Dz
turbulence caused by villous endarteritis activates coagulation which forms small blood clots that are in the pulmonary vessels; pieces of dead worm can also act like small clots
Pathophysiology of Pulmonary hypertension in HW Dz
decreased pulmonary blood flow due to enlargement of right ventricle that results in pressure buildup in pulmonary vasculature behind the right atria
Pathophysiology of ascites and hepatic congestion in HW Dz
right-sided heart failure
Pathophysiology of acute respiratory distress & dyspnea in HW Dz
disturbed blood flow to portions of the lungs makes lungs less efficient/able to do their job of gas exchange
Pathophysiology of caval syndrome in HW Dz
large # of worms spilling into right atrium & vena cava
Clinical signs of caval syndrome
Shock Intravascular hemolysis Hepatic/Renal Failure Ascites Extreme Exercise Intolerance
Caval syndrome pathophysiology of shock
secondary to disruption in the systemic blood circulation
Caval syndrome pathophysiology of Intravascular hemolysis
RBCs become more fragile and get damaged navigating around worms
Caval syndrome pathophysiology of hepatic/renal failure
due to decreased blood supply of the liver and hemoglobinuria damaging kidneys
Caval syndrome pathophysiology of ascites
pressure increase of venous circulatory system in abdomen –> venous hypertension –> leakage of fluid from vessels into peritoneal cavity
Caval syndrome pathophysiology of extreme exercise intolerance
lack of blood flow thru heart
Two HW tests and their purposes
- Antigen Test –> screening tool; looks for adult HW piece that body identifies as an antigen
- Modified Knott’s Test –> only if antigen test is positive; concentrates # of circulating microfilaria so they can be easily identified
Class 1 HW Dz
- CS
- Lab Data
- Rads
- Prognosis w/ Tx
asymptomatic to mild CS = none Labs = normal Rads = normal Prognosis = good
Class 2 HW Dz
- CS
- Lab Data
- Rads
- Prognosis w/ Tx
moderate
CS = intermittent cough +/- exercise intolerance
Labs = mild anemia
Rads = mild cardiomegaly, vessel enlargement
Prognosis = guarded
Class 3 HW Dz
- CS
- Lab Data
- Rads
- Prognosis w/ Tx
Severe
CS = persistent cough, exercise intolerance
Labs = anemia, hypoalbuminemia, proteinuria
Rads = cardiomegaly, tortuous pulmonary vessels, pulmonary infiltrates
Prognosis = poor
Class 4 HW Dz
- CS
- Lab Data
- Rads
- Prognosis w/ Tx
Caval Syndrome
CS = shock, collapse
Labs = severe anemia, hematuria, azotemia, elevated hepatic enzymes
Rads = cardiomegaly, tortuous pulmonary vessels, pulmonary infiltrates
Prognosis = grave
Treatment Plan for HW Dz
(28 days doxycycline to kill Wolbachia)
- adult worms residing in pulmonary vasculature and heart must be killed with an adulticide (Melarsomine)
- if microfilaria are present, kill them
- preventative plan for rest of dog’s life
How does the Tx plan differ if the P has caval syndrome?
must surgically remove HWs, have pet heal, and then P considered Class 3 and can begin adulticide Tx
What is the only FDA approved med for microfilaria therapy?
Advantage Multi
What nursing strategy is IMPERATIVE to follow post adulticide therapy?
strict cage rest for 4 weeks w/ bathroom breaks on a leash to prevent premature breaking up of worm bits from causing thromboembolism
Nursing Strategies for patients exhibiting pulmonary thromboembolism signs
O2 therapy
aspiring to decrease platelet function
corticosteroids to minimize inflammation
cage rest
Concepts dog owners should know and understand about HW Dz
a. Life threatening and preventable Dz
b. Annual antigen test because it’s dangerous to consider the pet safe
c. Give the owner a handout
i. Meds to be used
ii. How meds are given
iii. Side effects of each med
iv. Purpose of exercise restriction
v. What exercise restriction means
vi. How long exercise restriction will last
d. Untreated HW Dz will more than likely kill the pet, but treatment may also kill the pet
e. Pets not showing any clinical signs have best chance for survival
Prevention protocol will be established for the remainder of the pet’s life
