 |
Archive
|
Hot Topic
Lungworm
From November 2007 we are seeing more and more cases of lung worm in cats and dogs. It is appropriate to use the corect antiparasitic to prevent infestiation.
The following information was gathered from an external laboratory which we use to help us with diagnostics. It describes well how lung worm occurs and what it can do.
WHAT ITS CALLED, WHERE IT COMES FROM AND HOW IT DEVELOPS
Dogs contract Angiostrongylus vasorun infection by ingesting the L3 larvae in the intermediate host - slugs and snails -. The L3 larvae migrate to the mesenteric lymph nodes and mature into L5 larvae before migrating via the lymphatics, liver and caudal vena cava entering the right ventricle and pulmonary arteries by the 9thto 10th days after infection. Thread-like adults develop in the pulmonary circulation and deposit eggs in the terminal pulmonary capillaries. The eggs hatch, larvae then escape into the alveoli and bronchioles and are coughed up and passed into the faeces of the host where they are ingested by slugs and snails feeding on the faeces. The presence of adult nematodes in the lungs cause an immunological response which is the basis for many of the clinical signs and subsequent pathology of the disease. Crenosoma vulpis infection shows the same lifecycle but produces amild inflamatory response pressenting as a productive cough.
Aelurostrongylus abstrusus in the cat follows a relatively similar lifecycle with birds and rodents as intermediate hosts. However the presence of the adult worms in the airways can provoke an intense inflammatory response causing significant respiratory disease.
CLINICAL SIGN WHICH SHOW SUSPICION OF LUNGWORM CONTAMINATION
It is recommended that screening for lungworm should be undertaken when presenting signs include any of the following:-
Respiratory signs of coughing, dyspnoea, hyperpnoea, tachypnoea, ausculatory wheezing.
Cardiovascular signs:-tachycardia, subcutaneous oedema, limb swelling, ascites/pleural effusion.
Coagulation abnormalities:- prolonged bleeding, prolonged capillary refill time, haematochezia, subcutaneous haematoma, and signs of thromboembolic disease.
CNS signs:- Ataxia, incoordination, gait abnormalities.
DIAGNOSTICS WHICH LEAD TO FURTHER SUSPICION
Common haemogram abnormalities include:- thrombocytopenia, hyperglobulinaemia, eosinophilia, neutrophilia, and anaemia. Some clinical cases can have hypercalcaemia.
Thoracic radiographs can show abnormalities such as patchy alveolar interstitial pattern affecting the dorsocaudal lung fields, bronchial thickening and mild pleural effusions.
HOW TO PROVE IT IS LUNGWORM
Definitive diagnosis requires the demonstration of the L1 larvae in multiple feacal samples over a 7 day perios to allow for the intermittent nature of larvae shedding.
Larvae can also be demonstrated in BAL samples but false negatives are common.
TREATMENTS
There are three typical bands of prescription treatments where data sheets should be consulted for specific dosages. Supportive treatments should be used based on clinical signs. Severe dyspnoea and ascites may occurr post treatment necessitating the use of broncho-dilators, expectorants and/or diuretics for a short time.