Everyone looks forward to the rains. But along with happy moments, the season also brings with it flooded roads and an explosion in the mosquito population. During the rains, mosquitoes become extra active, and transmit several viral and parasitic infections which may lead to an epidemic. The mosquitoes suck blood that contains the virus or parasite from an infected person, and then inject it into the next person they feed on. This transmits the infection from one person to another.
Malaria is caused by two main species of parasites. The vivax malaria is usually a benign infection, whereas the falciparum species can cause a severe and complicated infection.
Symptoms: The patient feels intensely cold. This is followed by shivering and high-grade fever. The symptoms last a few hours and subside only to recur the next day or the day after, in a similar fashion. Sometimes, malarial fever can be continuous with intermittent shivering.
Complications: Though usually mild, the vivax type of malaria can be associated with a low platelet count. The falciparum infection can be complicated by severe anaemia due to the destruction of the red blood cells by the parasite, low platelet count and at times liver and kidney failure. The person may also lapse into a coma due to the involvement of the blood vessels in the brain.
Treatment: The vivax type responds to Chloroquine, whereas the falciparum infection is usually resistant to Chloroquine. Very effective drugs usually given as a combination (artemesenin combination therapy – ACT) work well for falciparum infections. Though prophylactic drugs taken regularly can prevent malarial infections, it is usually advised for visitors coming to India for a short period of time.
Preventive measures: The best defence against Malaria is to prevent breeding of mosquitoes. Insecticide impregnated mosquito nets and application of mosquito repellents are effective. Though the use of coils, mats and insect-repellent fumes is widespread in our country, their actual effectiveness in preventing malaria remains questionable.
Filariasis is another parasitic infection which, luckily for us, is becoming uncommon in India now.
Symptoms: The microfilaria or the young ones of the filarial worms in an infected person are sucked in by the mosquitoes and then injected into the victims. These may then mature into worms after passing through the various organs. The worms lodge themselves in the lymph nodes (usually in the thigh region) and gradually block the lymph vessels, thus producing the typical limb swelling referred to as ‘elephantiasis’. The limbs with blocked lymph channels may periodically get infected with bacteria. The result can be redness, pain and worsening of the swelling. The worms also release the microfilaria periodically resulting in high fever with severe shivering.
Complications: The long-term complications of this infection due to recurrent local limb infections can lead to grotesque disfiguring and disability.
Treatment: Though there are still no drugs available to effectively kill the adult worms, a combination of drugs, mainly de-worming agents and antibiotics, can effectively treat these infections and prevent the long-term complications. But still, a sure shot way to prevent these infections is avoidance of mosquito bites.
Japanese B Encephalitis
This infection is seen in certain parts of central and eastern India and is caused by a virus that is mosquito-borne.
Symptoms and Complications: Encephalitis or brain fever has no specific treatment. The management is purely supportive. The infection can sometimes have disastrous consequences that include permanent brain damage and death.
Treatment: There is a vaccine available worldwide, but unfortunately, this is not commercially available in India. The government makes the vaccine available during outbreaks.
The rise in dengue cases in our country is alarming. There are four types of dengue virus, and infection can be due to any one. Re-infections can lead to an exaggerated immune response with heightened complications.
Symptoms: High fever, severe body pain, lethargy, and pain behind the eyes are characteristic of Dengue. A diffuse red rash may be seen in some. Nausea and vomiting due to liver involvement may occur. Itching is common when the infection resolves.
Complications: There is a low white blood count initially, which recovers spontaneously. This is followed by a drop in the platelet count, which may drop to levels less than 10000 (Normal 150000 – 300000). Though most infections are harmless and resolve in 4 -5 days in spite of the low platelet counts, some may be associated with bleeding manifestations (from the gums, bowels or under the skin).
Fortunately, most patients tolerate even very low levels of platelets (10000) without any problems. More complications and sometimes death is seen in children. When the platelet count drops below 50000, the patient needs close monitoring. Platelet transfusions are advised only if there is active bleeding.
Treatment: There are no specific anti-viral agents, though a specific vaccine is showing good efficacy against a couple of types of these viruses.
Chikungunya is another viral infection transmitted by mosquitoes. Meaning ‘break bone fever’ in Swahili, it causes epidemic infections. The last major epidemic was over 5 years ago, but since then it has been known to cause sporadic infections in India.
Symptoms and Complications: There is a sudden onset of fever with severe pain in all the major joints which can incapacitate a person. The person is bed-ridden for 4-5 days before gradual recovery.
The joint pains may persist for several months and may require strong anti-inflammatory medicines. There is usually no residual joint deformity. In some cases, it can be a mild infection which completely settles in a few days. There have also been cases of brain fever due to Chikungunya.
Treatment: Treatment is with painkillers and anti-inflammatory medicines. Additional anti-arthritis medicines including steroids may be required when there is severe persistent joint pain. There is no vaccine for Chikungunya. The only preventive intervention is protection from mosquito bites.
- Prevent mosquito breeding by covering all water containers at home. Avoid rainwater stagnation in the garden, in tyres and containers.
- Use bed nets (repellant impregnated if available) and mosquito repellants.
- Wear trousers and full-sleeve shirts to cover arms and legs to prevent mosquito bites.
Dr V Ramasubramanian is a Consultant (Infectious Diseases) at Apollo Hospitals and Director, Boosters Adult Vaccination Centre & Travel Clinic.