KOCHI: A rare mosquito-borne disease that first surfaced in the state in 1976 has now been reported by a paediatrician here in a 12 -year-old girl who approached him with complaints of chest pain.
The disease called dirofilariasis (dog heart worm) is transmitted by mosquitoes from dogs to humans and has its larval form in dogs and adult form in the humans.
Dr. M. Narayanan, paediatrician with Ernakulam Medical Centre (EMC), on examining the child could make out a small swelling of around one cm diameter over the breast bone. All other findings were normal. The child was subjected to ultra sound examination by sinologist Dr.Ambily Chandran.
She detected a live worm in the swelling on the chest and suspected it to be dirofilariais. Later, the swelling was surgically removed by a team of Dr.P.S.Binu, paediatric surgeon of EMC. The worm was alive at the time of removal.
Dr. Elizabeth George, pathologist and Dr.Vinod Franklin, microbiologist, confirmed that it belonged to the species dirofilaria repens. “About 7-24 percent of domestic dog population in our state harbours this larva in their blood. The carriage rate in stray dogs has not been studied. The rate of carriage in them would be higher considering their increased exposure to mosquitoes. The larvae reach the mosquitoes when they bite the dogs. Majority of the mosquito species in Kerala - anopheles, culex and aedes- are capable of harbouring the larva,” says Dr Narayanan.
The mosquitoes carry the larvae from the dogs to the humans where they mature into adult worms. “Adult worms usually settle in the lungs, eyes and subcutaneous tissues and produce symptoms like cough, pain and swellings. When the lesions are in the subcutaneous tissues or eyes, diagnosis and surgical treatment are easier. When the worms settle in the lungs, detection and treatment are difficult. Chest X-rays of the worm lesion sometimes mimic lung cancer. Treatment of it is surgical removal of the worm with the surrounding tissue,” he says.
About 800 cases of dirofilariais have been reported worldwide. It rarely occurs in children. Dirofilariasis is considered as an emerging zoonosis (disease transmitted from animals to humans) of Kerala. “The abundance of domestic and stray dogs and the ubiquitous mosquito population provide an ideal situation for the worms to propagate. Mosquito control is the best preventive strategy,” says Dr Narayanan.
