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Questions and Answers
What is a potential risk of using macrocyclic lactones as a monotherapy in heartworm-positive dogs?
What is a potential risk of using macrocyclic lactones as a monotherapy in heartworm-positive dogs?
What surgical approach is suggested for removing heartworms from the right side of the heart?
What surgical approach is suggested for removing heartworms from the right side of the heart?
Vascular approach through a right-sided jugular approach
Which medications are recommended for preventing heartworm infection?
Which medications are recommended for preventing heartworm infection?
What is the role of Wolbachia in canine heart disease?
What is the role of Wolbachia in canine heart disease?
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Subcutaneous Dirofilariasis is primarily caused by D. immitis.
Subcutaneous Dirofilariasis is primarily caused by D. immitis.
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How long does it take for D. repens worms to mature?
How long does it take for D. repens worms to mature?
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The recommended dosage for milbemycin is ______ mg/kg.
The recommended dosage for milbemycin is ______ mg/kg.
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What size do female D. repens worms typically grow to?
What size do female D. repens worms typically grow to?
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What should be reviewed regarding Leishmania and Dirofilaria?
What should be reviewed regarding Leishmania and Dirofilaria?
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What are the clinical signs associated with Leishmania and Dirofilaria?
What are the clinical signs associated with Leishmania and Dirofilaria?
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What is the primary vector for Leishmania infantum?
What is the primary vector for Leishmania infantum?
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Leishmaniasis is mainly a disease of humans.
Leishmaniasis is mainly a disease of humans.
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What is the estimated number of dogs with Leishmaniasis in southwestern Europe?
What is the estimated number of dogs with Leishmaniasis in southwestern Europe?
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Which of the following populations are particularly susceptible to zoonotic infection?
Which of the following populations are particularly susceptible to zoonotic infection?
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What is the main purpose of DACTARI?
What is the main purpose of DACTARI?
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Which age groups show peak prevalence in Leishmania infection?
Which age groups show peak prevalence in Leishmania infection?
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Which immune cells do promastigotes invade in a mammalian host?
Which immune cells do promastigotes invade in a mammalian host?
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What is the most common abnormal finding on clinical examination of dogs with Leishmaniasis?
What is the most common abnormal finding on clinical examination of dogs with Leishmaniasis?
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What is the primary treatment for Leishmaniasis?
What is the primary treatment for Leishmaniasis?
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Leishmania is transmitted via _____ during feeding.
Leishmania is transmitted via _____ during feeding.
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What are sand flies most active?
What are sand flies most active?
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Vaccination can completely replace other preventative measures against Leishmania.
Vaccination can completely replace other preventative measures against Leishmania.
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What is the expected outcome for dogs exposed to Leishmania?
What is the expected outcome for dogs exposed to Leishmania?
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A cure for Leishmaniasis is likely.
A cure for Leishmaniasis is likely.
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What is a poor prognostic sign in dogs with Leishmaniasis?
What is a poor prognostic sign in dogs with Leishmaniasis?
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What was Frodo's breed?
What was Frodo's breed?
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What significant findings were revealed in Frodo's blood samples?
What significant findings were revealed in Frodo's blood samples?
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Dirofilaria immitis resides in the heart and pulmonary arteries.
Dirofilaria immitis resides in the heart and pulmonary arteries.
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What is the minimum age for dogs to start prophylaxis against Dirofilaria?
What is the minimum age for dogs to start prophylaxis against Dirofilaria?
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What are the common countries in Europe affected by Dirofilaria?
What are the common countries in Europe affected by Dirofilaria?
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Match the following clinical signs with their severity class:
Match the following clinical signs with their severity class:
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Heartworm is a zoonotic disease that commonly affects humans.
Heartworm is a zoonotic disease that commonly affects humans.
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The most common way to look for adult Dirofilaria is by using the __________ test.
The most common way to look for adult Dirofilaria is by using the __________ test.
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Adults worms reach sexual maturity at least 6 months after inoculation.
Adults worms reach sexual maturity at least 6 months after inoculation.
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What does thromboembolic event refer to in the context of Dirofilaria immitis?
What does thromboembolic event refer to in the context of Dirofilaria immitis?
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What method can be used to confirm cardiac changes in infected dogs?
What method can be used to confirm cardiac changes in infected dogs?
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What treatment option is mentioned for Dirofilaria immitis?
What treatment option is mentioned for Dirofilaria immitis?
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Killing adult worms does not carry any risks.
Killing adult worms does not carry any risks.
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Study Notes
Learning Objectives
- Understand the aetiology and pathophysiology of Leishmania and Dirofilaria.
- Identify clinical signs associated with Leishmania and Dirofilaria infections.
- Discuss diagnostic methods for Leishmania and Dirofilaria.
- Explore treatment options for infected dogs.
- Analyze preventative strategies for these parasites.
Leishmaniasis Overview
- Leishmaniasis is a protozoan disease affecting dogs (and occasionally cats), prevalent in South America, the Middle East, and the Mediterranean.
- Leishmania infantum is the primary causative agent in southern Europe, transmitted by Phlebotomus sand flies.
- Estimated 2.5 million dogs in southwest Europe have Leishmaniasis, with climate change facilitating spread northward.
Zoonotic Risks
- Low zoonotic risk exists; however, children and immunosuppressed adults (e.g., HIV patients) are particularly vulnerable.
- Concurrent infection with Ehrlichia is common in cases of Leishmaniasis.
Epidemiology
- Sand flies are absent in the UK, yet imported dogs from endemic areas have increased Leishmaniasis cases.
- PETS (Pet Travel Scheme) since 2000 has allowed numerous dogs from endemic regions into the UK without specific health checks for exotic diseases.
- DACTARI, initiated in 2003 for reporting Leishmaniasis cases, has limited effectiveness and has been discontinued.
Transmission
- Reports of Leishmaniasis in un-travelled dogs co-housed with infected animals, suggesting potential mechanical transmission or other unknown vectors.
Life Cycle
- Transmission occurs through female sand flies that inject Leishmania promastigotes into host skin during feeding.
- Promastigotes are engulfed by macrophages and multiply, leading to dissemination to visceral organs.
- Vertical transmission and blood transfusion cases have been documented in North America.
Clinical Signs
- Chronic and variable course; clinical signs may develop years post-infection.
- Common symptoms include exercise intolerance (67.5%), weight loss (64%), and lymphadenopathy (62-90% of affected dogs).
- Cutaneous signs, such as exfoliative dermatitis and abnormal nail growth, are notable; renal issues like proteinuria due to glomerulonephritis are also observed.
Diagnosis
- Sickness in dogs with overt signs of Leishmaniasis can be diagnosed via cytology, PCR, or serology.
- Laboratory findings often indicate chronic immune stimulation; increased globulins and decreased albumin are common.
- PCR is highly sensitive during acute infection but less so for chronic cases.
Treatment
- Leishmaniasis treatment aims to control symptoms rather than achieve a cure; success varies.
- Allopurinol is the main medication, often combined with meglumine antimoniate or miltefosine; significant side effects can occur.
- Domperidone has shown promise for improving immune response and clinical signs.
Prevention
- Canine vaccination against Leishmania is available and significantly reduces infection risk.
- Hygiene measures and protective collars can help prevent exposure to sand flies, particularly during peak activity hours at dawn and dusk.
Prognosis
- A cure for Leishmaniasis in dogs is unlikely; improvement is seen in many cases unless severe complications arise, especially renal failure.
Case Example - Frodo
- A 5-year-old Greyhound imported from Spain developed signs of lethargy and weight loss after 18 months in the UK.
- Clinical examination revealed significant skin lesions and an azotaemia associated with a protein-losing nephropathy.
- Positive serology for Leishmania and presence of amastigotes in macrophages confirmed the diagnosis, but treatment response was poor leading to euthanasia.### Dirofilariasis
- Adult Dirofilaria immitis typically inhabit pulmonary arteries and right ventricle, leading to potential vascular proliferation and narrowing, resulting in pulmonary hypertension and thrombosis.
- Microfilariae produced by adult worms enter the bloodstream and are transmitted mainly by mosquitoes, with over 70 species, including Aedes caspius, Aedes geniculatus, and Aedes punctor identified as competent vectors in Europe.
Worldwide Distribution
- D. immitis is widespread in North America and Southern Europe, but not endemic in the UK.
- In the USA, major infection areas are along the Gulf coast, Eastern Seaboard, and Mississippi river valleys.
- Risk factors include large male dogs housed outdoors, with infection signs typically appearing after 6 months of age; prophylaxis recommended starting at 8 weeks.
Lifecycle
- Infection begins when mosquitoes inject L3 larvae into dogs during a blood meal. These larvae mature into adults within the heart and produce microfilariae, which are further transmitted via mosquitoes.
Pathogenesis
- Dogs are primary hosts; zoonotic infections in humans are rare, typically involving only immature nematodes. Dead worms can lead to thromboembolic events mimicking severe diseases.
Clinical Signs
- Many infected dogs show minimal symptoms initially; signs may include coughing, weight loss, syncope, and dyspnea, especially if pulmonary arterial disease develops.
- Severity depends on worm burden, duration of infection, and host immune response.
- American Heartworm Society categorizes clinical severity into four classes, ranging from no symptoms to severe caval syndrome.
Caval Syndrome
- Results from a high worm burden obstructing the tricuspid valve, causing acute heart failure, hypotension, shock, and potential renal failure.
Diagnosis
- Blood tests may indicate eosinophilia; routine SNAP tests detect the presence of adult female D. immitis antigens.
- Microfilariae can be identified using blood smears or modified Knott's test; advanced cases may require radiographs and echocardiography to confirm cardiac changes.
Treatment
- Options vary based on worm burden; conservative care includes using corticosteroids and diuretics. Adulticide treatment may involve melarsomine, carefully administered to mitigate thromboembolic risks.
- Surgery may be necessary for worms obstructing heart structures, particularly in cases of caval syndrome.
Prevention
- Monthly chemoprophylaxis with medications such as milbemycin or selamectin is effective in preventing infection, even in collie breeds susceptible to MDR-1 abnormalities.
Wolbachia
- Wolbachia bacteria, symbiotic with D. immitis, may contribute to heart disease; doxycycline treatment could improve outcomes in infected dogs prior to adulticide therapy.
Subcutaneous Dirofilariasis
- Mainly caused by D. repens, transmitted by different mosquito species, this disease manifests in subcutaneous tissues rather than the heart, typically resulting in asymptomatic infections.
Completion of Learning Objectives
- Understanding the aetiology and pathophysiology of both Leishmania and Dirofilaria is essential for recognizing and treating these conditions effectively in veterinary practice.
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Description
Explore the global parasites Leishmania and Dirofilaria in this comprehensive lesson on Canine Infectious Diseases. Learn about their transmission via insect vectors, the regions they are endemic to, and their diagnosis in dogs. Perfect for veterinarians and students interested in parasitology and infectious diseases.
