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Questions and Answers
What is the adult length of female Dirofilaria immitis worms?
Which species act as intermediate hosts for Dirofilaria immitis?
What is a significant pathological effect of Dirofilaria immitis infection?
Which diagnostic method can be used to identify microfilariae in the blood?
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What is the primary method of treatment for adult Dirofilaria immitis?
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What is the role of microfilariae in the life cycle of Dirofilaria immitis?
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Which clinical sign is NOT associated with heartworm infection?
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What does the modified Knott's test involve?
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What is one main health risk associated with Dirofilaria immitis infection in humans?
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Which of the following best describes the life cycle of Dirofilaria immitis starting from the mosquito's bite?
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What role does Wolbachia pipientis play in the pathology of Dirofilaria immitis infections?
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What is the first larval stage of Dirofilaria immitis that is injected into the definitive host by a mosquito?
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What is an effective measure to reduce the risk of zoonotic transmission of Dirofilaria immitis?
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What is considered the definitive host for Dipetalonema reconditum?
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Which of the following accurately describes the adult morphology of Dipetalonema reconditum?
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What role do fleas play in the life cycle of Dipetalonema reconditum?
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Which diagnostic method can be used to differentiate Dipetalonema reconditum from Dirofilaria immitis?
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What is the significance of Dipetalonema reconditum being classified as non-pathogenic?
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What size are the females of Dipetalonema reconditum compared to the males?
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What preventative measures can be taken to control Dipetalonema reconditum infections?
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How long does it take for microfilariae to develop into infective L3 larvae within the flea or louse?
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What is the common name for Dracunculus insignis?
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What is the primary pathology associated with Dracunculus insignis?
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Which animal serves as a definitive host for Dracunculus insignis?
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How does Dracunculus insignis start its life cycle?
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What clinical sign is indicative of a Dracunculus insignis infection?
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How is Dracunculus insignis typically diagnosed?
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What is the treatment method for Dracunculus insignis infection?
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What type of organism serves as an intermediate host for Dracunculus insignis?
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What is the common name for Filaroides osleri?
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What is the typical size range for adult Filaroides osleri females?
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Which of the following describes the typical habitat of adult Filaroides osleri?
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Which clinical sign is commonly associated with Filaroides osleri infection?
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How is Filaroides osleri primarily diagnosed?
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What type of life cycle does Filaroides osleri possess?
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What therapeutic option is commonly used for treating Filaroides osleri infection?
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What serious issue can arise from nodules caused by Filaroides osleri?
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What symptoms are commonly observed in a Capillaria aerophila infection?
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Which hosts are definitive for Capillaria aerophila?
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What is the primary method used to diagnose Capillaria aerophila?
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What is a key characteristic of the eggs of Capillaria aerophila?
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How long does it typically take for the eggs of Capillaria aerophila to embryonate and develop into infective larvae?
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What method can be used to assess for Capillaria aerophila in the trachea?
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What is the treatment option for Capillaria aerophila infection?
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What potential public health concern is associated with Capillaria aerophila?
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What is the common name for Aelurostrongylus abstrusus?
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Which of the following accurately describes the definitive host of Aelurostrongylus abstrusus?
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What is the approximate prepatent period for Aelurostrongylus abstrusus?
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What is a common clinical sign associated with Aelurostrongylus abstrusus infection?
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Which of the following hosts can act as intermediate hosts for Aelurostrongylus abstrusus?
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What pathology is associated with Aelurostrongylus abstrusus infection?
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What method can be used to diagnose Aelurostrongylus abstrusus infection?
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Which of the following treatments is commonly used for Aelurostrongylus abstrusus infection?
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What is the primary treatment option for infections caused by Paragonimus kellicotti?
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Which of the following can help visualize cysts or fluid in the pleural cavity related to Paragonimus kellicotti infections?
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What zoonotic behavior is associated with Paragonimus kellicotti infections in humans?
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Which symptom is commonly associated with paragonimiasis caused by Paragonimus kellicotti?
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What preventive measure can help reduce the risk of Paragonimus kellicotti infection?
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What is the common name for Paragonimus kellicotti?
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Which animals are considered definitive hosts for Paragonimus kellicotti?
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What is the function of the first intermediate host in the life cycle of Paragonimus kellicotti?
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What is a significant impact caused by a heavy infection of Paragonimus kellicotti?
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What is the prepatent period for Paragonimus kellicotti?
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What clinical sign is associated with Paragonimus kellicotti infection?
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Which structure does Paragonimus kellicotti typically inhabit in its definitive host?
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What sequence describes a step in the life cycle of Paragonimus kellicotti?
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What is the common name for Pearsonema (Capillaria) plica?
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What is a distinguishing feature of adult Pearsonema plica?
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What are the definitive hosts for Pearsonema plica?
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How does Pearsonema plica complete its life cycle?
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Which clinical sign is commonly associated with a Pearsonema plica infection?
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What is a typical diagnostic method for identifying Pearsonema plica?
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Which treatment is commonly used for Pearsonema plica infection?
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What type of pathology is primarily associated with Pearsonema plica infection?
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What is the primary treatment for Dioctophyme renale?
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Which of the following best describes the preventive measures for Dioctophyme renale infection?
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What zoonotic risk is associated with Dioctophyme renale?
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In advanced cases of Dioctophyme renale, what diagnostic method may be required?
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Where can larvae from Dioctophyme renale migrate in humans?
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What is the common name for Dioctophyme renale?
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Which host is classified as an intermediate host for Dioctophyme renale?
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What clinical signs are most likely to arise if both kidneys are affected by Dioctophyme renale?
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What is the typical prepatent period for Dioctophyme renale?
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What pathology is primarily associated with Dioctophyme renale infections?
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How is Dioctophyme renale typically diagnosed in a host?
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Which of the following hosts can act as paratenic hosts for Dioctophyme renale?
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What larval stage develops in earthworms during the life cycle of Dioctophyme renale?
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What is a common method for treating Thelazia californiensis infections?
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Which of the following anthelmintics can be used to treat Thelazia californiensis infections?
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What is a preventative measure against Thelazia californiensis infections?
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What zoonotic risk is associated with Thelazia californiensis?
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What is an important hygiene measure to prevent the zoonotic transmission of Thelazia californiensis?
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What is the common name for Thelazia californiensis?
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What is a definitive host for Thelazia californiensis?
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Which stage in the life cycle of Thelazia californiensis is directly ingested by its intermediate host?
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What is the average prepatent period for Thelazia californiensis infection?
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Which clinical sign is associated with Thelazia californiensis infection?
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Which of the following methods is primarily used for diagnosing Thelazia californiensis?
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What condition can Thelazia californiensis lead to if left untreated?
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Which of the following describes the morphology of adult Thelazia californiensis?
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Study Notes
Common Name
- Dirofilaria immitis is commonly known as heartworm.
Adult Morphology
- Adult females can reach lengths of up to 30 cm.
- Adult males are approximately 15 cm long.
- These worms inhabit the right ventricle and pulmonary arteries of their hosts.
Hosts
- Definitive hosts include dogs, cats, ferrets, and rarely humans.
- Intermediate hosts are mosquitoes, mainly from Aedes, Culex, and Anopheles species.
Life Cycle
- Begins with a mosquito bite, transferring ingested microfilariae (L1) from an infected host.
- Within the mosquito, microfilariae develop into infective L3 larvae after 10-14 days.
- During a subsequent blood meal, the mosquito injects L3 larvae into a new host’s bloodstream.
- L3 larvae migrate to the heart and lungs where they mature into adults and produce circulating microfilariae.
Pathology
- Adult worms obstruct pulmonary arteries, leading to progressive pulmonary endarteritis and fibrosis.
- This results in decreased blood flow, chronic pulmonary hypertension, right heart failure, and potential vena cava syndrome.
Clinical Signs
- Common signs of heartworm infection include:
- Chronic progressive cough
- Exercise intolerance
- Fatigue
- Weight loss
- Ascites
- Severe cases may lead to death.
Diagnosis
- Diagnostic methods include:
- Identification of microfilariae in blood via direct smear or modified Knott's test.
- Antigen and antibody detection.
- Radiography to check for enlarged right heart and pulmonary arteries.
- Echocardiography and necropsy.
Modified Knott's Test
- Involves adding formalin to a blood sample, centrifuging it, staining the sediment, and examining for microfilariae.
- Dirofilaria microfilariae are larger, tapered, straight, and stationary compared to smaller Dipetalonema microfilariae, which have blunted anterior ends and curved bodies.
Treatment Options
- Treatment includes:
- Adulticidal drugs such as melarsomine.
- Microfilaricidal drugs like ivermectin.
- Surgical removal of worms and supportive care.
- Preventative measures involve routine use of chemoprophylaxis with ivermectin, milbemycin oxime, selamectin, and moxidectin.
Role of Wolbachia
- Wolbachia pipientis, a gram-negative bacterium, colonizes Dirofilaria immitis.
- It causes inflammation upon the death of the parasite by releasing antigens that stimulate the mammalian host's immune response.
- Doxycycline is effective against this bacterium.
Public Health Concerns
- Dirofilaria immitis can infect humans, leading to pulmonary dirofilariasis, which is often asymptomatic but may appear as lung nodules.
- Preventative measures in pets can reduce the risk of zoonotic transmission.
Detailed Life Cycle
- Life cycle involves a definitive host (dogs, cats, ferrets) and an intermediate host (mosquitoes).
- Mosquitoes ingest circulating microfilariae (L1) from infected hosts during a blood meal.
- Microfilariae molt inside the mosquito, developing into infective L3 larvae.
- Mosquitoes transmit L3 larvae into new hosts, where they migrate to subcutaneous tissues and molt into L4 larvae in 3-12 days.
- After 2-3 months, L4 larvae continue to develop into immature adults (L5) and migrate to the heart and pulmonary arteries.
- Adult worms mature approximately 6-7 months post-infection and begin producing circulating microfilariae (L1) to continue the life cycle.
Common Name
- Dipetalonema reconditum is often referred to as a non-pathogenic filarial worm of dogs, without a specific common name.
Adult Morphology
- Adults are small, thread-like worms residing in the subcutaneous tissues of dogs.
- Males measure approximately 4-5 cm in length.
- Females are larger, measuring around 6-7 cm.
Hosts
- Definitive host: Dogs.
- Intermediate hosts include fleas (Ctenocephalides felis) and lice (Heterodoxus spiniger).
Life Cycle
- Begins when a flea or louse ingests microfilariae (L1) during a blood meal from an infected dog.
- Inside the vector, microfilariae develop into infective L3 larvae over 7-10 days.
- When the vector bites another dog, L3 larvae are transmitted through the bite wound.
- Larvae migrate through the subcutaneous tissues, maturing into adult worms.
- Adults mate, and females produce microfilariae that enter the bloodstream.
Pathology
- Generally considered non-pathogenic; does not cause significant disease.
- Microfilariae may be present in the blood without causing clinical symptoms.
Clinical Signs
- Typically, there are no clinical signs associated with infection; regarded as non-pathogenic.
Diagnosis
- Diagnosis involves identifying microfilariae in the blood.
- Utilization of the modified Knott's test differentiates Dipetalonema reconditum from Dirofilaria immitis based on size, shape, and movement patterns.
Treatment and Prevention
- Treatment is usually not required due to the non-pathogenic nature.
- Microfilariae can be treated with ivermectin if necessary.
- Preventative measures focus on controlling flea and louse infestations in dogs.
Public Health Concerns
- No significant public health or zoonotic concerns exist as Dipetalonema reconditum does not infect humans.
Common Name
- Dracunculus insignis is commonly known as the North American Guinea Worm.
Adult Morphology
- Adults can reach lengths of up to 28 cm; males are significantly smaller.
- Worms typically inhabit the subcutaneous tissues of their definitive hosts.
Hosts
- Definitive hosts include dogs, cats, raccoons, mink, foxes, and skunks.
- Intermediate hosts are copepods, a type of small aquatic crustacean.
- Frogs can act as paratenic hosts, which may aid in the parasite's lifecycle.
Life Cycle
- Lifecycle initiation occurs when a definitive host ingests water containing infected copepods with L3 larvae.
- Larvae are released in the stomach and penetrate the intestinal wall, migrating to subcutaneous tissues to mature.
- After mating, females migrate to the skin, usually on lower limbs, to create a blister.
- Release of L1 larvae into water occurs when the blister touches water, enabling copepods to ingest and develop L3 larvae, completing the cycle.
Pathology
- Main issues arise from the female’s migration to the skin and blister formation, causing localized inflammation.
- This migration results in irritation and pain, impacting host wellbeing.
Clinical Signs
- Signs of infection include dermal ulceration as a result of blister formation.
Diagnosis
- Diagnosis relies on observing characteristic blisters and potentially visible worms under the skin.
- Microscopic fluid examination from blisters may reveal the presence of larvae.
Treatment and Prevention
- Treatment includes slow extraction of the worm, often requiring winding it around a stick or gauze over several days to prevent breaks.
- Ivermectin and other broad-spectrum anthelmintics may be prescribed.
- Prevention strategies focus on avoiding contaminated water, controlling access to infested water sources, and regular deworming.
Public Health Concerns
- Dracunculus insignis does not pose a direct threat to humans as it is not a zoonotic parasite.
- However, Dracunculus medinensis, a related species, does affect humans, making control in animal populations crucial for public health.
Common Name
- Filaroides osleri is commonly known as the canine lungworm.
Adult Morphology
- Adults are small, slender roundworms, with males measuring approximately 6 mm and females up to 13 mm.
- Adult worms reside in nodules located within the trachea and bronchi of the host.
Definitive Hosts
- The definitive host for Filaroides osleri is the dog.
Life Cycle
- The life cycle is direct, with adult worms laying eggs that hatch into first-stage larvae (L1) in the respiratory tract.
- L1 larvae are coughed up, swallowed, and expelled via feces, vomit, or bronchial secretions.
- L1 larvae are immediately infective when ingested by another dog through contaminated food, water, or contact with an infected dam.
- After ingestion, larvae migrate through the intestinal wall, enter the bloodstream or lymphatics, and travel to the lungs to mature into adults.
Associated Pathology
- Infection causes bronchitis and formation of nodules in the trachea and major bronchi, which may obstruct airways and cause breathing difficulties.
- The irritation and inflammation can result in chronic coughing and other respiratory issues.
Clinical Signs
- Common signs include chronic coughing, dyspnea (labored breathing), stridor (wheezing), emaciation, and anorexia.
- Severe cases may present respiratory distress due to airway obstruction.
Diagnosis
- Diagnosis involves detecting larvae in feces through direct fecal smears.
- Larvae may also be recovered from sputum or via transtracheal wash (TTW) and bronchoalveolar lavage (BAL).
- Bronchoscopy allows direct visualization of the nodules in the trachea and bronchi.
Treatment and Prevention
- Treatment includes anthelmintics such as albendazole; surgical excision may be necessary in severe cases.
- Preventative measures involve isolating infected animals to limit the spread of larvae, particularly in kennels.
Public Health Concerns
- Filaroides osleri poses no significant public health or zoonotic concerns as it does not infect humans.
Common Name
- Capillaria aerophila is commonly referred to as the bronchial capillarid.
Adult Morphology
- Adults measure about 2-3 cm in length.
- Characteristically slender, with a whip-like shape.
- Found primarily in the trachea and bronchi of hosts.
Definitive Hosts
- Definitive hosts include domestic dogs, cats, and wild mammals like foxes.
Life Cycle
- Direct life cycle with no intermediate hosts.
- Adult females lay eggs in the lungs, which are expelled by coughing, swallowed, and excreted in feces.
- Eggs are single-celled, featuring bipolar plugs and a textured surface.
- Eggs embryonate over 5-7 weeks, developing into infective L1 larvae inside the egg.
- Larvae hatch in the intestines upon ingestion and migrate to lungs via bloodstream.
- Paratenic hosts, such as earthworms, can aid in the cycle.
- Prepatent period is approximately 40 days.
Pathology
- Infections cause irritation in trachea and bronchi, leading to tracheitis and bronchitis.
- Heavy infestations can lead to chronic inflammation and respiratory distress.
Clinical Signs
- Possible symptoms include chronic cough, wheezing, nasal discharge, and severe difficulty breathing.
- Many infections are asymptomatic and detected incidentally.
Diagnosis
- Diagnosis often made through fecal flotation tests, identifying characteristic eggs.
- Eggs can also be retrieved via transtracheal wash (TTW) or bronchoalveolar lavage (BAL).
Treatment and Prevention
- Treatment includes broad-spectrum anthelmintics like fenbendazole or ivermectin.
- Preventive measures focus on sanitation to minimize environmental contamination with eggs.
- Reducing exposure to contaminated environments is advised, particularly due to rare human cases.
Public Health Concerns
- Very rare zoonotic risk associated with Capillaria aerophila, with isolated human infection cases reported.
Common Name
- Aelurostrongylus abstrusus is commonly known as the feline lungworm.
Adult Morphology
- Adult worms measure approximately 0.7-1.0 cm in length.
- Typically reside in the lung parenchyma of infected cats.
Hosts
- Definitive hosts (DH): Cats.
- Intermediate hosts (IH): Snails and slugs, which harbor L3 larvae.
- Paratenic hosts (PH): Birds, rodents, amphibians, and reptiles that can also carry L3 larvae.
Life Cycle
- The life cycle is indirect.
- Adult worms in the lungs lay eggs that hatch into first-stage larvae (L1) within the lungs.
- L1 larvae are coughed up, swallowed, and excreted in feces.
- Larvae penetrate or are ingested by snails or slugs, developing into L3 larvae.
- Cats become infected by consuming either snails/slugs or paratenic hosts that have ingested infected mollusks.
- L3 larvae migrate from the intestines to the lungs through the bloodstream, maturing into adults.
- The prepatent period lasts approximately 6 weeks.
Associated Pathology
- Infection leads to the formation of subpleural nodules in the lungs, which trigger an inflammatory response.
- Potential complications include chronic bronchitis, interstitial pneumonia, pulmonary edema, lung consolidation, and respiratory failure.
Clinical Signs
- Many infections are asymptomatic.
- Possible clinical signs include chronic cough and dyspnea (labored breathing).
Diagnosis
- Diagnosis can be difficult due to the low concentration of larvae in feces.
- The Baermann technique is used to recover larvae, though sensitivity can be low.
- Diagnosis may also involve direct fecal smears, radiography for lung changes, and detection of larvae in sputum, transtracheal wash (TTW), or bronchoalveolar lavage (BAL).
Treatment and Prevention
- Treatment options include anthelmintics such as fenbendazole or ivermectin.
- Preventative measures involve keeping cats from hunting or eating snails, slugs, and paratenic hosts.
Public Health Concerns
- There are no known zoonotic risks associated with Aelurostrongylus abstrusus, as it does not infect humans.
Common Name
- Paragonimus kellicotti is commonly known as the North American lung fluke.
Adult Morphology
- Adult flukes measure approximately 1 cm in length.
- They inhabit the lungs of definitive hosts within cystic structures in the lung parenchyma.
Hosts
- Definitive hosts (DH): dogs, cats, and occasionally humans.
- First intermediate host (IH): a snail, where early larval development occurs.
- Second intermediate host (IH): a crayfish, where the fluke develops into the infective metacercarial stage.
Life Cycle
- Adult flukes in the lungs produce eggs that are coughed up, swallowed, and excreted in feces.
- Eggs hatch into miracidia upon reaching water, which infect the first intermediate host (snail).
- In the snail, miracidia develop into sporocysts, rediae, and then cercariae.
- Cercariae exit the snail to infect crayfish, encysting as metacercariae.
- Definitive hosts become infected by consuming raw or undercooked crayfish.
- After ingestion, metacercariae excyst in the intestines, penetrate the intestinal wall, and migrate to the lungs to mature into adults.
- Worms typically form pairs in the lungs about 3 weeks post-infection.
- The prepatent period lasts around 5-6 weeks.
Pathology
- Infection leads to inflammation and granuloma formation in the lungs, causing cystic structures.
- Young flukes incite eosinophilic inflammation, necrosis, and cellular infiltrates around them.
- Cysts can interfere mechanically with breathing and, in severe cases, cause pulmonary hemorrhage, pleuritis, and lung abscesses.
Clinical Signs
- Common symptoms include coughing, malaise, fever, and in severe cases, pulmonary hemorrhage.
Diagnosis
- Diagnosis involves identifying characteristic eggs in sputum or feces using sedimentation techniques.
- Radiographic imaging may reveal distinct lung cysts, while thoracic ultrasound helps visualize cysts or pleural fluid.
Treatment and Prevention
- Treatment options include praziquantel or fenbendazole to eliminate adult flukes.
- Prevention strategies involve avoiding the consumption of raw or undercooked crayfish and controlling crayfish exposure to pets.
Public Health Concerns
- Paragonimus kellicotti is zoonotic, capable of infecting humans, mainly through undercooked crayfish.
- Infected individuals may develop paragonimiasis, presenting chronic cough, chest pain, and other respiratory symptoms.
Common Name
- Pearsonema (Capillaria) plica is commonly known as the bladder worm.
Adult Morphology
- Adults are thin, thread-like worms, measuring 1 to 6 cm in length.
- Typically found embedded in the mucosa of the urinary bladder or other parts of the urinary tract.
Hosts
- Definitive hosts include dogs, cats, and various wild mammals.
- Intermediate hosts are earthworms, which harbor the infective larvae.
Life Cycle
- Eggs containing first-stage larvae (L1) are excreted in the urine of the definitive host.
- Earthworms ingest these eggs, and larvae develop into infective L3 larvae within their connective tissue.
- When a definitive host consumes an infected earthworm, larvae are released in the digestive tract and penetrate the intestinal wall.
- Larvae migrate to the kidneys and urinary bladder, mature into adults, and embed in the bladder mucosa, resuming egg production.
- Prepatent period lasts about 60 days.
Pathology
- Causes irritation and inflammation of the bladder wall, potentially leading to chronic cystitis.
- Chronic irritation may result in discomfort and increase susceptibility to secondary bacterial infections.
Clinical Signs
- Often mild or asymptomatic, but can manifest as:
- Cystitis
- Stranguria (painful urination in small volumes)
- Pollakiuria (frequent urination)
- Hematuria (blood in urine)
- Incontinence
Diagnosis
- Diagnosis is made by identifying characteristic eggs in urine sediment.
- Eggs are bipolar, lemon-shaped, with a rough shell, distinguishable through microscopic examination.
Treatment and Prevention
- Treatment involves anthelmintics such as ivermectin or fenbendazole.
- Preventative measures include:
- Avoiding ingestion of earthworms.
- Controlling environments where pets urinate and play.
- Regular deworming and maintaining proper sanitation.
Public Health Concerns
- No significant public health or zoonotic concerns since Pearsonema plica does not infect humans.
Common Name and Morphology
- Dioctophyme renale is commonly known as the giant kidney worm.
- It is one of the largest parasitic nematodes, with females up to 1 meter long and males measuring 20-40 cm.
- The worms exhibit a red coloration and usually inhabit the kidneys, favoring the right kidney specifically.
Hosts
- Definitive hosts include dogs and other carnivores, notably mink.
- Earthworms serve as intermediate hosts, while paratenic hosts consist of fish and amphibians, such as frogs.
Life Cycle
- Life cycle begins with unembryonated eggs excreted in the urine of definitive hosts.
- In aquatic settings, eggs embryonate and develop into first-stage larvae (L1).
- Ingestion of these eggs by earthworms allows larvae to hatch and mature into infective third-stage larvae (L3).
- Paratenic hosts may become infected by consuming earthworms, where larvae can encyst in tissues.
- When a definitive host consumes an infected intermediate or paratenic host, larvae migrate from the stomach to the liver and then to the kidneys, maturing primarily in the right kidney.
- The prepatent period for development to adult is approximately 5-6 months.
Pathology
- The large size and migrating behavior cause significant pathology, including the destruction of renal parenchyma.
- Only a thin renal capsule remains if the kidney is significantly damaged.
- Bilateral infections can lead to uremia and potential renal failure.
- Rupture of the renal capsule may result in peritonitis due to worms entering the abdominal cavity.
Clinical Signs
- Clinical signs can be absent with unilateral kidney involvement, as the other kidney compensates.
- Severe cases or bilateral infections may show signs of uremia, leading to fatigue and nausea.
- Peritonitis is a risk if the renal capsule ruptures.
Diagnosis
- Diagnosis often involves identifying eggs in urine sediment.
- Imaging techniques like ultrasound or radiography can indicate kidney damage or enlargement.
- In advanced cases, exploratory surgery may be necessary for both diagnosis and treatment.
Treatment and Prevention
- The main treatment is surgical removal of the affected kidney (nephrectomy).
- Effective anthelmintic treatments for adult worms are lacking.
- Preventive measures include avoiding raw or undercooked fish and amphibians and preventing pets from drinking untreated water.
Public Health Concerns
- Dioctophyme renale is zoonotic and can infect humans via consumption of undercooked or raw paratenic hosts.
- In humans, larvae can migrate inappropriately, forming encapsulated subcutaneous nodules where they cease development.
Common Name
- Thelazia californiensis is commonly known as the eye worm.
Adult Morphology
- Adult eye worms are small, thin nematodes, measuring up to 15 mm in length.
- They are primarily found in the conjunctival sac and lacrimal ducts of the eye.
Hosts
- Definitive hosts include dogs, cats, deer, sheep, and humans.
- Intermediate hosts are mainly flies from the Diptera order, which serve as vectors for the larvae.
Life Cycle
- The life cycle starts when adult females produce first-stage larvae (L1) in the eye of the host.
- L1 larvae are released into the tear film and ingested by flies when they feed on tears.
- Within 2-4 weeks in the fly, the larvae develop into infective third-stage larvae (L3).
- L3 migrate to the fly's mouthparts, where they are deposited back into the conjunctival sac of a new host during feeding.
- The larvae mature into adults in the new host, completing the cycle.
- The prepatent period lasts about 3-6 weeks before mature adults are present.
Associated Pathology
- Infection leads to irritation and inflammation of the eye, causing conjunctivitis and keratitis.
- Symptoms include excessive tearing, squinting, photophobia, possible corneal ulcers, and secondary bacterial infections.
Clinical Signs
- Key clinical signs are excessive tearing (epiphora), conjunctivitis, squinting, photophobia, and visible worm movement in the eye.
- Severe infections may result in corneal ulcers and secondary bacterial infections.
Diagnosis
- Diagnosis is confirmed by direct observation of worms in the conjunctival sac or on the eye's surface.
- Slit-lamp examination can help visualize smaller worms.
- Larvae may be detected in tear fluid or conjunctival swabs using a microscope.
Treatment and Prevention
- Treatment includes manual removal of worms with fine forceps under local anesthesia.
- Anthelmintics like ivermectin or milbemycin oxime are used to eliminate remaining worms.
- Antibiotics may be used for secondary bacterial infections.
- Preventive measures involve controlling fly populations and minimizing exposure to flies during peak seasons.
Public Health Concerns
- Thelazia californiensis is zoonotic and can infect humans, leading to similar ocular symptoms.
- Human infections are linked to contact with infected animals or exposure to the same fly species.
- Adopting proper hygiene and protective measures can help reduce the zoonotic transmission risk.
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Description
This quiz explores the morphology, life cycle, and hosts of Dirofilaria immitis, commonly known as heartworm. It examines the adult size differences between male and female worms, as well as the various species that serve as definitive and intermediate hosts. Perfect for veterinary students and animal health professionals.
