A Guideline for Dengue Fever in Pakistan
What is Dengue Fever?
It is a disease caused by one of the four flavivirus strains (DENV-1, DENV-2, DENV-3 and DENV-4) spread by the mosquito Aedes aegypti. The disease causes high fever and has been called “break bone fever” because of the joint aches and muscle pains it causes. Dengue viruses can also cause a potentially fatal disease, dengue hemorrhagic fever, in people who have previously been infected with a different strain of the virus.
The patient gets lifetime immunity to the strain which infects him but he remains susceptible to the other three types.
Any subsequent infection with other subtypes of Dengue virus can result in deadly complications of Dengue Hemorrhagic fever or DSS.
A few words about its transmitter; the Aedes Aegypti Mosquito?
The mosquito Aedes Aegypti if bites a patient of Dengue fever, gets the virus from his blood. If this mosquito then bites a healthy person it can transmit the disease.
This mosquito lives in or around houses.
It breeds in tiny fresh water collections in small pots, tyres, junk etc.
This disease is transmitted by aged mosquitos, so there is a point in decreasing the life span of mosquito.
These mosquitos have short flight zones and do not travel long distances.
These are day time biters and are especially ferocious at dawn and dusk.
How to control breeding of mosquito.
Avoid small fresh water collections in and around your house.
Spray insecticides or pour a few drops of kerosine oil over such water collections to destroy mosquito eggs and larvae.
In our set up the usual presentation is that of a mild to moderate illness. 50 Percent cases go unnoticed as a mild non specific infection. The disease is milder in children.
Incubation Period = 3-14 Days.
Dengue Fever: (DF)
Presents as a common viral febrile illness with more body aches and pains.
Fever usually lasts for 3-7 days.
It then usually gets completely cured.
In some case the fever is followed by a 2-3 days afebrile period after which one of the two dreaded complications occur. These are DHF and DSS.
Dengue Hemorrhagic Fever (DHF)
In addition to features of DF the patient may have bleeding from his mouth, nose, skin, in stools or in vomiting.
Abdominal pain, excessive restlessness, confusion, decrease in body temperature, and a drop in the platelet count are other indicators of imminent DHF.
Dengue Shock Syndrome. (DSS)
The blood pressure of patient falls dramatically due to vascular leakage in some patients and patient may go into shock. This is a clinical emergency and immediate intravenous fluid replacement is must.
- Clinical features may vaguely point to diagnosis especially in the presence of similar cases in vicinity or patient travelling to any place where there is an outbreak.
- Tourniquet Test: To perform the test, pressure is applied to the forearm with a blood pressure cuff inflated to between systolic and diastolic blood pressure for 10 minutes. After removing the cuff, the number of petechiae in a 5 cm diameter circle of the area under pressure is counted. Normally less than 15 petechiae are seen.
- Decreased WBC count
- Decrease Platelets Count
- Increase Hematocrit
- IgM Abs (ELISA) in suspected cases
- ALT is almost universally high.
There is no specific treatment for Dengue.
- For fever give paracetamol but not aspirin.
- For shock plenty of oral and intravenous fluids must be given to keep the blood pressure normal. There is nothing specific to choose between crystalloids and colloids as studies have shown both to be equally effective.
- There is no specific role of antibiotics.
- Role of Antiviral agents is still experimental.
Future Research Prospects
Till today no vaccine has been prepared and the challenge is that any candidate vaccine must impart full immunity to all the four virus types otherwise the risk of complications goes high.
An Australian research focuses on infecting Aedes Aegypti with bacterial parasite Wolbachia. This bacteria hampers the egg laying capability of Female mosquito thereby controlling the breeding.
In a Malaysian Experiment 6000 Genetically Engineered Male Aedes mosquitos were set free in Cayman Islands. These males on mating with females are likely to produce short lived offsprings. This experiment has said to reduce the mosquito population by 80% in one year.
A fresh water crustacean which eats the larvae of Aedes Aegypti is also being studied.