Dictyocaulosis of sheep, cattle and protostrongylidosis of small ruminants. Flashcards
(60 cards)
What are the final hosts of Dictyocaulus viviparus?
Cattle, llamas, alpacas.
Where is Dictyocaulus viviparus located in the host?
Lower respiratory tract — bronchi, trachea.
Responsible for parasitic bronchitis.
What is the size of Dictyocaulus viviparus?
3–8 cm
Describe the eggs of Dictyocaulus viviparus.
Medium, oval, 80–100 μm, 2 thin shells, embryonated L1 inside, light grey.
Describe the morphology of adult Dictyocaulus viviparus.
- Slender, thread-like worm.
- Mouth surrounded by 3 lips.
- Male has bursa copulatrix.
Describe the life cycle of Dictyocaulus viviparus.
Eggs coughed up, swallowed, and L1 hatches from the egg during this passage and is released in the feces.
After 24 hours, L1 → L2. L2 is enclosed within the old L1 cuticle until it molts to L3.
L3 (infective stage) climbs grass in in early hours or cool climates and is ingested by the final host with feed.
Host ingests L3 → penetrates intestinal wall → enters lymphatic vessels, molts to L4 in mesenteric lymph gland (in 4 days), then migrates via lymph & blood vessels to the lungs → stays in alveolar capillaries
L4 breaks through into air passages, and matures into adults in the bronchi in 4 weeks.
Direct life cycle.
What is the pathogenesis of Dictyocaulus viviparus infection in cattle?
The pathogenesis varies depending on:
- Location in the respiratory tract
- Number of infective larvae
- The immune status of the animal
In cattle, the prepatent phase involves bronchiolar blockage by eosinophilic infiltrates in response to developing larvae, leading to airway obstruction and collapse of alveoli distal to the block. Some cattle may die during this stage (eosinophilic bronchitis).
Prepatent phase: Larvae appear in the alveoli, causing bronchiolitis and bronchitis. Heavily infected calves can die before adult worms appear due to respiratory failure.
Patent phase: Thousands of adult worms in lumen of the bronchi, and dark red, collapsed lung areas are observed around infected bronchi. This condition is termed parasitic pneumonia.
Postpatent phase: Recovery after adults worms are expelled. However, inflammatory reactions and lung lesions may persist for weeks or months.
What clinical signs are seen in Dictyocaulus viviparus infection?
Signs range in severity depending on worm burden:
- Mild to moderate: Coughing, slightly increased respiratory rate
- Severe: Persistent coughing, progressive respiratory distress, respiratory failure, tachypnea, open-mouth breathing, drooling, and prominent lung sounds
Systemic signs include:
- Reduced weight gain
- Reduced milk yield
- Weight loss, particularly in cattle
What is the epidemiology of Dictyocaulus viviparus infection?
Typically only affects calves in their first grazing season.
Older cattle usually have strong aquired immunity on endemic farms.
Larvae can overwinter (if not too cold).
What drugs are used to treat Dictyocaulus viviparus?
Benzimidazoles, Ivermectin.
How is Dictyocaulus viviparus infection controlled?
Use of vaccination or anthelmintics.
Oral vaccination (Europe): 2 doses, 4 weeks apart; second dose given 2 weeks before grazing.
How is Dictyocaulus viviparus diagnosed?
Fecal exam (larvoscopy)
Can be seen in Sputum or nasal discharge
ELISA
Where is Dictyocaulus viviparus geographically located?
Distribution: Worldwide
Also known as: lungworm
What is the final host of Dictyocaulus filaria?
Small ruminants — sheep and goats.
Where is Dictyocaulus filaria found in the host?
In the bronchi and trachea.
What is the size and morphology of Dictyocaulus filaria?
Males: 4–8 cm
Females: 6–10 cm
White worms. The posterior end is blunt.
What is the pathogenesis of Dictyocaulus filaria?
Causes catarrhal, eosinophilic bronchitis.
The number of lungworms per animal is generally low, so widespread lesions are uncommon.
Pulmonary oedema and emphysema can occur on lung surface, and may be studded with purulent areas due to secondary bacterial infections.
What are the clinical signs of Dictyocaulus filaria infection?
Coughing
Unthriftiness (poor growth or condition)
Dyspnea (difficulty breathing)
Tachypnoea (rapid breathing)
Nasal discharge
What is the epidemiology of Dictyocaulus filaria?
Prevalent worldwide
Sporadic outbreaks occur, only in temperate countries
In temperate areas, epidemiology resembles that of D. viviparus
More frequent in Eastern & Southern Europe, the Middle East, and India
What treatments are effective against Dictyocaulus filaria?
Ivermectin and Fenbendazole.
How can Dictyocaulus filaria be controlled?
Annually treatment of flock with anthelmintics in late pregnancy.
Graze ewes & lambs on pastures that were not used by sheep the previous year, especially in temperate areas.
How is Dictyocaulus filaria diagnosed?
- Based on history, anamnesis & Clinical signs
- Examination of fresh feces
- Necropsy (lung pathology)
What order does lungworms of cattle and small ruminants belong to?
Strongylida.
Where is Dictyocaulus filaria found geographically?
Worldwide
