With the impending monsoon various kinds of vector-borne diseases loom large over Nepal
As monsoon begins, there is an increasing threat of vector-borne diseases in Nepal. Vectors are living organisms that transmit infectious diseases from humans to animals and vice-versa. These vectors are usually blood-sucking insects that ingest diseases during a blood meal from infected humans or animals and inject it into new hosts. Mosquitoes, flies, sand flies and ticks are common disease vectors found in southern region of Nepal, causing Malaria, Kalazar, Filariasis (Elephantitis), Japanese Encephalitis (JE), among other infectious diseases.
There are several other new vector-borne diseases, the majority of them unfamiliar to healthcare providers. Chikungunya virus, West Nile virus, Chandipura Virus, Scrub typhus are recently uncovered vector-borne diseases, while Crimean-Congo hemorrhagic fever and Zika virus are suspected to have been circulating in Nepal for long. These potentially dangerous emerging infectious diseases seem to be largely ignored in Nepal.
With the impending monsoon various kinds of vector-borne diseases loom large over Nepal.
I had first reported about Chikungunya virus in a scientific journal in 2013 as patients from Dhading district were found to have the virus. Later, another research confirmed that it was circulating in Nepal, and may have existed for many years. India has been suffering from this virus for over a decade. But health care providers in Nepal have not included this virus in diagnosis.
Fever and joint pain are the most common symptoms of Chikungunya infection. Headache, muscle pain, rashes, joint swelling are other symptoms. Aedes agypti and Aedes albopictus mosquito species are main vectors. Both mosquito species are present in Nepal. Specific treatment is not available, while vaccine is under development.
West Nile virus was first discovered in Nepal in 2010 in fever-patients in Bharatpur and Kathmandu. Serious complications include high-grade fever, neck stiffness, tremors, seizures, muscle weakness, paralysis, and it can be fatal if untreated. No specific anti-viral medicine is available. Thus early diagnosis is a must to prevent serious complications. Culex mosquitoes are the vectors responsible for transmission of this virus. This mosquito is also involved in transmission of lymphatic filariasis (Elephantiasis) in Nepal. Therefore, it can be assumed that physicians in Nepal may have been underestimating its possible outbreaks.
Cases of acute encephalitis syndrome (AES) from unknown causes were reported in Udayapur, Saptari, Sunsari and Morang in 2014. They were later confirmed as Chandipura virus. Chandipura was first detected in Nagapur of India, where there had been an outbreak of febrile illness. Since then, Chandipura virus has been identified as a causative agent in several viral encephalitis outbreaks in different parts of India. Acute onset of fever, altered sensorium, seizures, diarrhea, vomiting are the main symptoms. Death or recovery can occur within two to three days of the first attack. Fifty percent or even higher death rate was reported in case of Chandipura virus outbreaks in India. Sanfly and Aedes Agypti mosquitoes are the vectors for this virus. Both are found in Nepal. Sandfly also acts as vector for Kalazar, and Aedes Agypti for dengue.
Scrub typhus was found to be spreading in different parts of the country in October 2015. It was noticed in hundreds of patients who had non-specific fever illnesses. Of these, nearly a dozen patients died. A scientific report published in 2004 talked of the existence of this bacterium in Nepal. Scrub typhus is another vector-borne disease transmitted by the bite of infected mite known as "Chigger". They are infected by feeding on the body fluid of mammals including mouse/rat and pass the infection to humans.
Symptoms generally appear between five to 20 days after the bite. Sudden onset of fever with chills, severe headache, red eyes and rashes on the trunk are common symptoms of Scrub typhus. An Eschar (a hard or dark scrab/crust or falling away of dead skin) can be present anywhere on the body, but may not always be visible. Severe pneumonia and Acute Respiratory Distress Syndrome (ARDS) are common after infection. Scrub typhus usually occurs during the rainy season, although it was widely reported in post-monsoon season last year. The new rainy season is nearly upon us. We must, therefore, be cautious about possible outbreak of Scrub typhus this time around as well.
Crimean Congo Hemorrhagic Fever (CCHF) is a viral disease transmitted by the bite of infected tick. It can also occur through contact with blood of infected cattle, goat, and sheep. Farmers are more vulnerable to this infection which can also spread through blood or body fluids of infected patients. Health care providers are therefore at risk during treatment in healthcare settings. Indeed, there have been several reports of CCHF transmission to health care providers from infected patients in developed as well as developing countries. So far there has been no documented CCHF infection in Nepal, which may be because there is no widely available test for CCHF.
As slaughterhouses in Nepal don't maintain good hygiene, butchers are at high risk of contracting CCHF. Sudden fever, joint pain, back pain, red eyes, red spots on the palate are common symptoms. Uncontrolled bleeding at injection sites can occur and complications may lead to respiratory, liver or kidney failures. CCHF outbreaks also occur during the rainy season—usually between June and September.
Zika Virus continues to spread to new territories worldwide. It was first noticed as a cause of microcephaly in newborn babies in Brazil in 2015. It is transmitted by the mosquito called aedes agypti that also spread dengue and chikungunya viruses. In Nepal, dengue usually occurs in during post-monsoon season, and hence it is reasonable to assume that Zika might also spread during this time if it enters Nepal.
It is difficult to detect Zika because symptoms are mild and patients may not seek treatment on time. Mild fever, skin rashes, red eyes and joint pain are the main symptoms. Majority of physicians have no idea where to send blood samples for testing, while on the other hand there are no comprehensive guidelines for precautionary and preventive measures. There is no treatment protocol and rehabilitation center for Zika patients either.
There has been little study on these diseases in Nepal. Since these diseases are vector-borne, they are generally active and seen during monsoon and post-monsoon seasons. These diseases could result in sudden epidemics in Nepal, but still go unrecognized in early stages. We should thus develop appropriate precautionary measures. Given the abundance of dangerous vectors in Nepal, Nepal could witness unpredictable human loss from these little known but dangerous diseases. This new threat of vector-borne infectious diseases must be considered while developing our health policies.
The author is Coordinator of the Clinical Research Unit, Sukraraj Tropical and Infectious Disease Hospital