Vector unit in Kota Star

DHO Kota Star
Date: 12 January 2009
Group A

Today we gathered at the vector unit at 8.30 a.m. We were then briefed regarding the morning activity of the vector unit. Today they were going to Kampung Bukit, Pokok Sena to look for Aedes mosquito breeding ground in the locality. The journey took approximately an hour. Upon reaching there we begin taking samples from various areas. These included old tires and large collections of water. We first search for the larvae then upon spotting them the PKA would use a pipette to collect these larvae. We found larvae in one of the old tires in one of the houses we surveyed. The larvae were placed into a bottle and sealed. The bottle was subsequently labeled. After collecting the sample the source of the larvae is usually empited to kill all remaining larvae. If this is not possible then abate (temephos) is added to the water. The unit can compound the owner of the house where the larvae was found. The compound is RM 300 I sporadic cases or RM 500 if the area is an area of epidemic. However in this case the owner was not compounded because it was a 1st offence. However the unit issued a warning where they listed the activities which should be done in order to avoid a compound when the unit comes back 7 days later for a follow up visit. There are separate forms to fill for warning and compound. We then went back to the DHO for further work.

Searching for larvae in old tyre

A few larvae were found



Mosquito larvae

The form on the right is a warning notice and on the left is the form which is filled if the owner is to be compounded.

After lunch we visited the lab in the vector unit. The unit is headed by En.Shariff, whom is an expert in identifying mosquito and larvae types. The morning collection will be sent here. We the saw how the slides containing the larvae were prepared and mounted. PKA Shariff then showed us the difference between the various types of mosquito and larvae. The following are the differences between larvae

The chart above differentiates between A.aegypti and A.albopictus
Morphology of the different types of mosquitos

• Absence of a siphon and presence of palmate hairs – Anopheles
• Short and conical shaped siphon and having teeth and hooks – Mansonia
• Short siphon with 1 ventral hair tuft on each side of the siphon – Aedes
• If the comb teeth have has lateral denticles – Aedes aegypti
• Comb teeth has no lateral denticles – Aedes albopictus
• Siphon has more than 1 hair tuft – Culex

These species carry various types of diseases –

• Anopheles - malaria
• Mansonia - filariasis
• Aedes aegypti - dengue
• Aedes albopictus – chikungunya, dengue
  
• Culex – encephalitis

There was however a rare type of larvae which was discovered. It was the Toxorhynchites type. These larvae feed on other larvae.

After the identification of the larvae, we proceeded to the join the unit for the evening fogging. The unit 1st started by preparing the material nedded for fogging. There are three chemicals used in the fogging. These include –
•Aqua
o Active ingredient - bioallethrin, permetherin, piperonyl butoxide
o It is of water base and mainly used within the houses.
•Mos spray
o Active ingredient - bioallethrin, permetherin, piperonyl butoxide
o It is diesel based and used primarily outside the house
•Malathion
o Used in the (Ultra low volume)ULV
o Usually done after Aqua & Mos spray

Planning in the DHO

The unit is at the Taman Setia Jaya flats - preparing

This fogger is spraying Mos spray

This fogger is spraying Aqua

The reason to do fogging in a particular area is – presence of a case in the area, breateau index > 5 or a aedes index > 2%.
Breateau index = number of larvae containing containers x 100 / number of premises inspected
Aedes index = number of house with larvae / number of premises surveyed x 100%

Then a meeting was conducted to brief the staff involved regarding the map and the procedure. The operations were led by En . The fogging was going to be conducted in the flats of Taman Setia Jaya. The area had a massive number of dengue cases from the start of the year. Upon arrival, we begun by inspecting the surrounding area. It was very dirty – there was rubbish everywhere, drains were clogged and many containers with water inside them. We begun by identifying the blocks in the area. Then we brought out the foggers and filled them with petrol and the insecticide. Then we begin fogging from house to house with Aqua Resigen. The surroundings were sprayed with Mos Spray. The disappointing part of the event was that almost 50% of the houses which were supposed to be fogged were locked. This may cause the failure of the projects and a waste of thousands of ringgit. While fogging, 6 banners were put up to inform the people in the area that their area was declared an area of epidemic.
An area is defined as an epidemic if there are 2 cases within the same locality, 2 cases within 400 meters distance and there is an epidemiological relationship between cases.
Other than fogging on foot the ULV was also patrolling and spraying malathion into the air. The operation was completed around 8.00 p.m.

Banners being put up to indicate to residents that this was an outbreak area. The surrounding is also very dirty with rubbish just being dumped everywhere