Overview mosquito-borne diseases
Mosquitos are known to cause more human suffering than any other organism in the world. According to the American Mosquito Control Association, a scientific/educational, not-for-profit public service association founded in 1935, more than one million people die worldwide from mosquito borne diseases every year. Mosquito-borne diseases are those diseases which are transmitted to humans through the bite of infected mosquitos. They not only carry diseases which affect humans but are quite capable of transmitting several diseases and parasites to dogs and horses as well. There is quite a long list of the common illnesses which one gets from mosquito bites. Here is a closer look at each of them.
What are mosquito-borne diseases?
The mosquito, which is Spanish for ‘small fly’, is an insect which belongs to the Culicidae family. There are thousands of mosquito species and the diseases carried and transmitted by such organisms are known as mosquito-borne diseases. The diseases spread by these organisms can be originally due to a parasite, as in the case of malaria, or by viruses, as in the case of Zika fever. Multiple factors like urbanization, global travel and growth in human population have increased the risk of mosquito-borne diseases. The most common types of mosquito-borne diseases are:
- Yellow fever
- Zika virus
- Japanese Encephalitis
- Lymphatic Filariasis
Dengue fever is a viral infectious disease carried by the bite of Aedes mosquito. The disease is caused by any of the four related dengue viruses, such as DEN-1, DEN-2, DEN-3, and DEN-4. Dengue fever is also called break-bone fever because it sometimes causes severe muscle and joint pain that feels like bones are breaking.
Symptoms of Dengue:
Exact symptoms of Dengue fever depend on age and usually start with fever within 4-7 days after a person has been bitten by an infected mosquito. The most common symptoms of classic dengue include:
- High fever, up to 105ºF
- Severe muscle and joint pain
- Severe headache
- A red rash that starts on the chest, back or stomach and spreads to the limbs and face
- Pain behind the eyes
- Nausea and vomiting
Treatment of Dengue:
Getting enough rest and treating the symptoms with fluids and pain relievers are the only things you can do in case of dengue. Sometimes it can lead to hemorrhagic fever, in which the small blood vessels leak and fill up fluid in the belly and lungs. In such cases, medical care is needed right away.
Malaria is a life-threatening mosquito-borne blood disease caused by a parasite called Plasmodium, which is transmitted to humans via the bites of infected Anopheles mosquito. In the human body, the parasites multiply in the liver, and then to red blood cells.
Symptoms of Malaria
Symptoms of Malaria is divided into two categories: Uncomplicated Malaria and Severe Malaria.
In uncomplicated malaria, the following symptoms progress through hot, cold, and sweating stages:
- Sensation of cold with chills or shivering
- Headaches, fever and vomiting
- Sometimes, seizures occur in younger individuals
- Sweats, followed by a return to normalcy (in temperature) with fatigue or tiredness
If laboratory or clinical evidence points towards dysfunction of vital organ, it is severe malaria. Severe malaria symptoms include:
- Fever and shivers/chills
- Impaired consciousness
- Respiratory distress and deep breathing
- Multiple convulsions
- Signs of anaemia and abnormal bleeding
- Evidence of vital organ dysfunction and clinical jaundice
Treatment of malaria
Treatment consists of medications like antimalarials and antibiotics. People also take antimalarial drugs before, after or during a trip to places where malaria is common.
The word, ‘Chikungunya’ means ‘to walk bent’. Fever and joint pain are significant symptoms of chikungunya. The Chikungunya virus is predominantly transmitted by a bite from an infected female “Aedes aegypti” Most often, chikungunya virus is spread to people by Aedes albopictus and Aedes aegypti mosquitoes. While generally it is not considered contagious, in some rare cases, Chikungunya virus can be transmitted through contact with an infected person’s blood. The disease can only definitively be diagnosed by a blood test and there are no vaccines available for it.
Symptoms of Chikungunya
While the incubation period of chikungunya disease is between 2-6 days, the symptoms usually start appearing 4-7 days post-infection. Other classic symptoms include:
- High fever (40 °C or 104 °F) which typically lasts for two days and then ends abruptly
- Viral rashes on the trunk or limbs
- Joint pains affecting multiple joints (for as long as two years)
- Other non-specific viral symptoms such as headache, loss of appetite, etc.
Treatment of Chikungunya
There is no treatment , but most people recover from this condition. Rest, fluids and pain relievers, non-steroidal anti-inflammatory drugs and analgesics are used for treatment
At present, Yellow fever occurs only in tropical areas of the Americas and Africa. It has both jungle and an urban cycle. It is a rare travellers’ illness now because many countries have regulations and mandates yellow fever vaccination prior to entering the country. While it does not occur in Asia, every year, close to 200,000 cases are reported with 30,000 deaths (with 90% occurring in Africa) in 33 countries.
The virus is primarily transmitted to humans through the bite of infected Aedes ( Haemagogus species) mosquitoes. Mosquitoes get infected with the virus by feeding on infected primates (human/non-human) and then can spread the virus to other primates (human/non-human). While most of the people infected with yellow fever virus have only mild illness or no illness, approximately 15 percent of cases that do show symptoms progress to develop a more serious form of the disease.
Symptoms of Yellow Fever
- Yellow-ish skin and eyes
- High fever accompanied by:
Severe symptoms include:
- High fever
- Failure of multiple organs
Treatment of Yellow Fever
There is no specific treatment for yellow fever. Efforts are aimed at managing symptoms and preventing complications. Oral rehydration therapy is one such way
The Zika virus is also spread through the bite of an infected Aedes mosquito – the same mosquitoes that spread chikungunya as well as dengue viruses. Zika virus primarily occurs in tropical and sub-tropical regions of the world. Majority of people infected with the Zika virus do not show signs or symptoms. However, when symptoms do occur, they generally begin with 2 to 7 days after a person is bitten by the infected mosquito.
Symptoms of Zika virus
Symptoms of the Zika virus commonly include:
- Mild fever
- Joint or muscle pain
Other symptoms may include:
- Pinkeye (conjunctivitis)
Most people recover fully and the symptoms resolvie in about a week. However, it is more severe in pregnant women as it can cause birth defects like small heads and brain damage in the babies.
Treatment of Zika Virus
Treatment is targeted at relieving the symptoms with rest, fluids and medications like acetaminophen. There is no vaccine to prevent this disease currently
Japanese Encephalitis is the most significant cause of viral encephalitis in Asia. Usually, it occurs in the rural or agricultural areas, often linked to rice farming. Japanese Encephalitis virus is spread to humans through the bite of infected Culex mosquitoes (Culet Tritaeniorhynchus, in particular).
While, most Japanese Encephalitis virus infections are mild with fever and headache, or without obvious symptoms, roughly 1 in 250 cases results in severe disease.
Symptoms of Japanese Encephalitis
Severe symptoms include:
- Rapid onset of high fever
- Severe Headache
- Neck stiffness
- In some severe cases, paralysis and coma
The case-fatality rate can be as high as 30 percent among those with disease symptoms
Treatment of Japanese Encephalitis
This can be self-healing or the underlying cause may be addressed. The treatment includes antiviral drugs and anticonvulsants, bed rest, fluid intake and symptomatic relief.
Lymphatic Filariasis, also known as elephantiasis, is caused due to parasitic worms and spreads into humans through mosquito bites. This tropical and parasitic disease severely affects the lymph nodes and vessels.
The common name is deduced from the fact that this disease leads to the swelling up of arms and legs to a great extent. The skin of the affected area turns thicker and harder, resembling that of an elephant. This disease is mostly found in people who reside in tropical and subtropical areas. So, here’s knowing more about this lymphatic condition.
Symptoms of Lymphatic Filariasis:
Most people who get this disease will not show clear symptoms, in spite of the damage caused to the lymph system. The parasite damages the lymph system. A small percentage of persons may develop lymphedema or, men may develop hydrocele, a swelling of the scrotum.
Lymphedema occurs from improper functioning of the lymph system which results in fluid collection and swelling. This affects the legs mostly, but can also occur in the genitalia, breasts and arms. Many individuals develop these clinical manifestations years after being infected. A few people also develop Tropical Eosinophilia .
Treatment of Lymphatic Filariasis
The main objective of treatment of an infected person is to kill the adult worm. Diethylcarbamazine citrate (DEC), which is both microfilaricidal and active against the adult worm, is the drug of choice for lymphatic filariasis. Ivermectin is effective against the microfilariae, but has no effect on the adult parasite