Verminous Bronchitis (Parasitic Bronchitis)

Verminous Bronchitis (Parasitic Bronchitis) is a lung worms disease of domestic animals includes cattle, horse, donkey, cat, dog, pig, sheep and goat.

Verminous bronchitis in cattle (Dictyocaulus viviparous)

Epidemiology

• Bovine parasitic bronchitis is a sporadic and unpredictable disease, because immunity develops more quickly than other nematodes.
• Disease is common in temperate countries due to high rainfall, prevent desiccations of the larvae.
• Disease is more common in young calves.
• Wind borne field-to-field transmission of larvae of lung worm by Pilobolus sporangiae, which is common in cattle faeces.
• The fungus Pilobolus may accumulate larvae of D. viviparous on the upper face of the spornangium, which when it explodes may propel the larvae as far as 3 meters.
• little migration of larvae from the faecal pads on to herbage, except during heavy rainfall.

Life cycle and transmission

Pathogenesis & clinical signs

Pathogenesis & clinical signs depends on location of larva within the respiratory tract, number of larva ingested and animal’s immune status.

Prepatent phase

• It is associated with blockage of many respiratory bronchioles with an eosinophilic exudates in response to developing larva, this results in obstruction of the airways and collapse of alveoli distal to the block.
• Clinically associated with tachypnea, coughing and animal may die due to development of severe interstitial emphysema.

Patent phase

• Lasting from days 25 to 55 is associated with adult parasite in the bronchi and trachea.
• The severe damage to the epithelium of bronchi causes, marked exudation and blockage of air passages.
• Development of chronic nonsuppurative eosinophilic granulomatous pneumonia in response  to eggs and larvae aspirated into the bronchioles and alveoli, leading to consolidation of lung lobules.
• Death is due to interstitial emphysema, pulmonary edema and secondary bacterial infections.

Late prepatent phase

• Epithelialization of the alveolar epithelium and hyaline membrane formation occur.
• Animals show dyspnea and coughing, with rapid loss of condition.
• Harsh respiratory sounds with bronchi and emphysematous crackling can be heard.
• Complication include pulmonary oedema and emphysema.

Postpatent phase

• It is a recovery stage.
• Respiratory rate decreases, coughing is less frequent and weight gain is resumed.
• Larvae which reach the lungs are destroyed by the immune response with the formation of lymphoreticular granulomas or nodule results in bronchiolar obstruction.

Diagnosis

• Based on the clinical signs and post mortem examination.
• Presence of first stage larva in the faeces. larva usually not found in faeces during prepatent and post patent phase.
• Bronchoscopy and radiography may helpful to find the  larva and lesions in the bronchi.
• Recovery of larva by Baermanns technique.

Differential diagnosis

• Epizootic bronchitis
• Viral pneumonia
• Pasteurella infection

Treatment

• Ivermectin, doramectin,eprinomectin and moxidectin, fenbendazole, oxfendazole and albendazoles are effective against all stage of D.viviparous.
• Ivermectin 200 µg/Kg.
• Fenbendazole – 5.0 mg/kg.
• Albendazole – 7.5 mg /kg.
• Oxfendazole – 4.5 mg/kg.
• Levamisole @ 7.5 mg/Kg  effective against immature worm,  second dose repeated 2 weeks later.
• Diethylcarbmazine – 22 mg/kg intramusculary for three days or a single dose of 50 mg/kg is primarily effective against the immature parasites.

Control

• Grazing management should be improved.
• Provide clean pasture for young calves.
• Animals continuously exposed to infection are at little risk provided the rate of acquisition of the infection is sufficient to stimulate a satisfactory immunity and not enough to cause clinical illness.
• Prophylatic anthelmintic treatment reduces pasture contamination.
• Vaccination: Two doses of 1000 irradiated larvae given at 4 weeks interval.
• Age of immunization – two months or older and exposure of infection is avoided until two weeks after second dose.

Verminous bronchitis in sheep and goat

Etiology

• Dictyocaulus filaria, Mullerius capillaris and protostongylus rufescens.

Transmission

• Infective Dictyocalus filaria larvae found on grass and ingested during grazing.
• M. capillaris and P. rufescens are transmitted when molluscan intermediate host are accidentally ingested by grazing animals.
• Lambs 4-6 months of the age are most severely affected, but sheep of all age groups are susceptible.

Life cycle

• Similar to D. viviparous in cattle.

Pathogenesis

• Presence of live larvae in bronchi, producing catarrhal parasitic bronchitis.
• The inflammatory process spreads to the surrounding tissues and exudate frequently passes back into the bronchioles and alveoli cause atelectasis and catarrh or pneumonia.
• Secondary bacterial infection leads to extensive areas of pneumonia.

Clinical manifestation

• It is usually chronic in nature.
• The animal may coughed up and tenacious mucus exudes from the nostrils, but cough is not always present.
• Dysponea is obvious signs.
• Rapid respiration.
• Abnormal lung sounds on auscultation.
• Temperature is not elevated unless pneumonia develops.

Necropsy Finding

• Localized and cone shaped area of pneumonia, accompanied by atelectasis and compensatory emphysema.

Diagnosis

• Presence of first stage larvae in fresh faeces.
• Eggs may found in the sputum or nasal discharge.
• Bronchoscopy and Radiography-to find lesions in bronchi and lungs.

Treatment

• Ivermectin, doramectin, eprinomectin and moxidectin, fenbendazole, oxfendazole and albendazoles are effective against all stage of D.filaria.
• Ivermectin 200 µg/Kg.
• Fenbendazole – 5.0 mg/kg.
• Albendazole – 7.5 mg /kg.
• Oxfendazole – 4.5 mg/kg.
• Levamisole @ 7.5 mg/Kg  effective against immature worm,  second dose repeated 2 weeks later.
• Diethylcarbmazine – 22 mg/kg intramusculary for three days or a single dose of 50 mg/kg is primarily effective against the immature parasites.

Control

• Animal must be removed from infected ground, placed on dry pastures and supplied with clean drinking water.
• Moist pastures must be avoided for grazing.
• Older animals should not be grazed together with the young stock.
• Vaccine – irradiated attenuated infective larvae used as vaccine.

Verminous bronchitis in pig

Etiology

• Metastrongylus apri (M.elongatus), M. Salmi and M.Pudendotectus.

Transmission

• Transmitted by ingestion of earthworm intermediate host.
• Age : Pigs at 4-6 months of age are highly susceptible.
• Verminous bronchitis and pneumonia are possibly due to secondary bacterial infection.
• Larvae of lung worm carry the swine influenza and swine fever virus.
• Larvae may transmit viruses of Teschen disease.

Life cycle

• The eggs are excreted through faeces, hatching of egg in soil and release the L₁ Larvae, which is ingested by earth worm and L₂ and L₃ developmental stage, occur in earth worm.
• Pig infected by ingestion of infected earth worm. Further development inside the pig is similar to D.viviparous.

Clinical signs and lesions

• Marked reduction in growth rate.
• Barking cough and pneumonia.
• Presence of greyish nodule near the ventral border of diaphragmatic lobe.

Diagnosis

• Based on the demonstration of embryonated eggs in fresh faeces.

Treatment

• Ivermectin, moxidectin and doramectin are recommended for lung worm infection in pigs.
• Levamisole 15 mg/ kg b.wt.
• Tetramisole 15 mg/ kg b.wt.
• Fenbendazole 20-30 mg/kg b.wt.

Control

• Infected pigs should be kept on dry ground or in sites with concrete floor and their faeces should be disposed off in such a way that they do not spread the infection.
• Young pigs should run on clean fields.
• Infected paddocks and fields may remain infected for a considerable time, since the intermediate stage can be in the earthworm for an unknown period.
•  A  3 % solution of carbathion applied in soil to kills earthworm.