| Probe |
august-september, 2020 | The Health
11
Know your viruses
as the larvae can still survive despite the
space spraying activity. The best preventive
measure is to keep the environment clean
and free from mosquito breeding sites,” said
Dr Noor Hisham.
Awareness
The Malaysian Medical Association (MMA)
believed the dengue problem could be
reduced significantly with increased
education and awareness campaigns,
regular monitoring and enforcement from
the authorities and through the collective
responsibility of the public.
Its president Dr N Ganabaskaran said
awareness campaigns during the 70s and
80s were very effective in communicating
preventive measures against the breeding of
the Aedes mosquito.
“At the time, municipal authorities used
to go from house to house checking if there
were any breeding grounds of the Aedes
mosquito and steep fines were issued to
house-owners.
“These simple enforcement steps led to
many people regularly checking their homes
for stagnant water which could potentially
become breeding grounds for Aedes
mosquito.
“We don’t see such measures being taken
these days. People wait for the authorities to
conduct fogging,” he shared.
Besides the local authorities, how do
Members of Parliament in Kuala Lumpur
for example, play their part with the local
authorities in fighting dengue?
The Health sent queries to three
MPs – Teresa Kok (Seputeh), Hannah Yeoh
(Segambut) and P. Prabakaran (Batu). “My
office has always contacted Kuala Lumpur
City Hall (DBKL) once we receive complaints
about the spike of dengue cases in certain
areas in my constituency," shared Kok,
adding that they have also been working
with DBKL in “gotong-royong” to help to
Alternative dengue treatment
While drug companies are looking for a
cure for dengue, research has also been done
on alternative forms of treatment to fight the
virus. It involves the use of natural ingredients
such as plants and other food items.
One standard traditional method is
using the Carica papaya tree leaf extract.
It is believed that the juice extracted from
the papaya leaf can help increase the blood
platelet count – something much-needed by
dengue fever patients.
In April 2013, this was confirmed in a study
by the Institute of Medical Research (IMR)
where 228 patients were tested. Half of the
patients with dengue fever (DF) and dengue
haemorrhagic fever (DHF) received the Carica
Papaya leaf juice (CPLJ) for three consecutive
days while the other half received treatment
clean up wastes and rubbish in areas that
have dengue cases. Yeoh and Prabakaran did
not respond.
Dr Noor Hisham informed the MOH had
intensified the awareness campaigns on
dengue at national, state and district levels
through health education sessions and slots
in television, radios as well as in social media.
“Also, dengue control should not be the
burden of the MoH alone,” reminded Dr
Norazman.
“At times, our resources are stretched
due to the high number of cases, such as in
2019. We need continuous support from the
public.”
He acknowledged that public
participation was vital in the fight against
dengue.
“The Public Health Department is
always ready to do its part, but if the public
is ignorant and do not take care of their
surroundings, dengue control efforts will be
futile.
Dengue management during Covid-19
Dr Noor Hisham also assured government
hospitals could treat dengue patients even
during the peak of the Covid-19 pandemic in
mid-April.
“There are 147 Ministry of Health (MoH)
hospitals with an overall capacity of 43,006
beds, including 872 ICU beds in 64 MoH
hospitals with ICU facilities.
“We have reduced the number of elective
admissions such as elective surgery to
reserve non-Covid-9 beds for acute and
critical cases, including dengue.
He said currently, many of our hospitals
have resumed their normal functions
following the reduction of Covid-19 active
case admissions.
“Many of hospital beds allocated for
Covid-19 cases have been released for
non-Covid-19 cases, including dengue,” he
said. — The Health
without the juice.
Their full blood count was monitored for
48 hours, and it showed that there was a
significant increase in mean platelet count
observed in the intervention group. However,
the same could not be said for the other half.
The study concluded that CPLJ does increase
the platelet count in patients infected by DF
and DHF.
That being said, CPLJ is not to be used to
replace actual treatment. As there is no real
cure for dengue, it is up to us to manage our
symptoms with the prescribed medicines,
drink lots of water and let our immune system
do its job.
Dengue patients must seek their doctor’s
advice and keep up with their medication for a
full recovery.
Dengue should not be taken lightly. The
virus is as deadly as the Covid-19 virus.
Even so, there are significant differences
between the two viruses. One may wonder
how both viruses differ.
Dr Norazah Ahmad, the Head of Infectious
Disease Research Centre (IDRC) from the
Institute for Medical Research (IMR), helped
throw some light on the differences.
She said the dengue virus (DENV) comes
from a different family from Covid-19 virus.
DENV is from family Flaviviridae, while Covid-19 virus is from the
family Coronaviridae.
“DENV causes dengue fever while SARS-CoV-2 or otherwise
known as Severe Acute Respiratory Syndrome coronavirus
2 (SARS-CoV-2) causes coronavirus disease (Covid-19),” Dr
Norazah explained.
DENV has four serotypes: DENV1, DENV2, DENV3 and DENV4.
“Following a primary infection with one dengue virus serotype,
protection against the infecting serotype (homotypic protection)
is considered long-lasting. Temporary cross-protection is induced
to the other serotypes (heterotypic protection), lasting up to two
years,” said Dr Norazah.
However, for Covid-19, there is SARS-CoV-2 which is spreading
globally and has undergone several mutations.
“The antibody response to SARS-CoV-2 is still under study.
It is still unknown whether the antibody can induce long-lasting
protection. A few studies showed that the antibody wanes after a
few months,” she explained.
How the dengue virus spreads
Dengue is transmitted by mosquitoes (mosquito-borne
infection), with female Aedes aegypti mosquitoes as their
primary vector and A. albopictus as a secondary vector.
“Mosquitoes mainly acquire DENV by feeding on the blood
of an infected human. DENV first infects and replicates in the
mosquito midgut epithelium.
“It subsequently spreads to the salivary glands of the mosquito
at approximately 7-10 days at ambient temperature.
“Once in the saliva, DENV can be inoculated into a human host
when the mosquito acquires a blood meal, thus spreading the
disease.”
She further explained that after human inoculation via the
bite of an infected female mosquito, the virus replicates in local
dendritic cells and subsequently enters the bloodstream.
Dengue viruses primarily infect macrophages, monocytes, and
dendritic cells. Haematogenous spread is the likely mechanism for
infection of peripheral organs. However, the SARS-CoV-2 is not
spread by a mosquito bite. Close human contact transmits it via
salivary or nasal fluids droplets.
“The virus binds to host cells by attraction with angiotensinconverting
enzyme 2 (ACE2) expressed in lower respiratory tract
cells.”
Treatments
At present, there is no drug treatment for both DENV and
Covid-19. Preventing transmission remains the best method;
vector control for DENV and physical distancing, wearing a mask
and practice hand hygiene for Covid-19.
According to Dr Norazah, the Aedes mosquitoes could evolve
and develop resistance to fogging insecticides over time. At
present, the IMR and the State Health Office are monitoring the
resistance status of Aedes in Malaysia.
“Through our research, we found there was resistance for
pyrethroid and organophosphate insecticides in Aedes if the same
insecticide was frequently used for fogging in certain localities.”
The resistance of Malaysian Aedes to pyrethroids and
organophosphates insecticides, is, however, highly localised in
specific areas only, thus we can still control the Malaysian Aedes
population.
However, new and innovative strategies such as Wolbachia
mosquitoes, Sterile Insect Techniques and Integrated Vector
Control are being used for dengue control.
When asked if we are any closer to a dengue vaccine, Dr
Norazah said that the first licensed dengue vaccine is CYD-TDV.
“This is a live attenuated, recombinant tetravalent vaccine. The
use of this vaccine has revealed an excess risk of severe dengue in
seronegative vaccine recipients compared to seronegative nonvaccinated
individuals while confirming long-term protection in
seropositive individuals. WHO`s interim recommendation posted
on Dec 22, 2017 was to vaccinate seropositive individuals only”.
She adds that there are two dengue vaccines that are currently
in Phase 3 clinical trials. These vaccines are also tetravalent
vaccines.