Dr Zubair Ahmad Dar
The major source of zoonotic infections are dogs. Dogs tranmit different types of viral, bacterial, protozoan and helminth infections to humans. These infections can be transmitted by infected saliva, aerosols, contaiminated urine or faeces and direct contact with the dog.
Dogs have been kept as pets for over 14 centuries. Owing a dog as pet can increase the activity of pet owners. Some studies have demonstrated that pet owners suffer from depression and mental stress less and have higher self esteem compared to others.
Although dogs have several positive effects on the psychological and psychical health of their owners, many diseases among human are attributed to them like Rabies, Echinococcosis (hydatid cyst), Toxoplasmosis and Toxocariasis. Children and immuno compromised individuals are especially at an increased risk of developing zoonotic infections. The increase in the population of stray and semi-domestic dogs has increased the risk of zoonotic diseases. The current topic focusses on a zoonotic disease in humans known as Toxocariasis which if ignored proves fatal in case of humans.
What is Toxocariasis
Toxocariasis is an infection transmitted from dogs to humans by the parasitic roundworms commonly found in the intestine of dogs (Toxocaracanis)and cats (Toxocaracati).
Prevalence of Toxocariasis in humans
Anyone can become infected with Toxocara. Young, children, pet owners have a higher chance of becoming infected.The rate of seroprevalence of Toxocara infection is found higher in higher age groups and as per the research work conducted by me during year 2005-2006 about32.86% of the children population and 40.78% of the adult population had Toxocarasero prevalence in Kashmir valley.
Risk of infection
Dogs and cats that are infected with Toxocara shed Toxocara eggs in their faeces which remain viable for longer period in soil and develop into infectious stages within a period of 3 weeks to several months and if infected objects like dirt, vegetables etc are accidentally swallowed a person gets infected.
Clinical manifestations of Toxocariasis
Persons infected with Toxocara infection may suffer from Ocular Toxocariasis/ ocular larva migrans(OLM) : it is usually caused by single larva entering the eye and it leads to decrease or loss of vision, retinal detachment, strabismus at leukokoria, photophobia, floaters, retinochorioditis, optic papillitis and endopthalamitis.
Visceral larva migrans/ visceral toxocariasis: it is characterized by clinical signs of fever, hepatomegaly and cough due to varying degrees of pulmonary infiltration.
The term covert toxocariasis has been used to desirable clinical syndrome with non specific signs including abdominal pain, anorexia, vomiting, nausea, limb pains and fever
How serious is Toxocara infection
In general although Toxocara infections are not so serious and many people especially adults who are infected with small number of larva may not notice infection may become severe. The most severe cases are more likely to occur in young children who often play in dirt or eat dirt or pica, eat uncooked/ unwashed vegetables and drink unboiled water.
Treatment of Toxocariasis
VLM is treated with anthelmintic drugs.OLM is more difficult to treat and usually requires prolonged steroid therapy and sometimes requires surgical removal of larva from eye of an infected person.
Prevention of toxocariasis
To be safe we should
Deworm pets so as to check basic source of infection
Wash hands with soap and water after playing with pets or other animals or attending work in fields
Properly wash raw vegetables before eating.
Drink boiled water
Avoid habit of eating dirt/ pica or geophagia in children
Stop entry of stray dogs in house yards by proper fencing and checking out the presence of pets in houses helps to decrease the rate of Toxocara infection.
Policy makers, planners should also create such an environment in and around public places, schools, playgrounds etc so as to check the entry of stray dogs in these areas and making humans less susceptible to the infection.
Dr Zubair Ahmad Dar