VECTOR-BORNE DISEASES: DENGUE
Vector-borne diseases are human diseases caused by vector-borne diseases such as parasites,
viruses and bacteriai. More than 700,000 deaths a year are caused by malaria, dengue,
schistosomiasis, human African trypanosomiasis, leishmaniosis, chagas disease, yellow fever,
and onchocercoses. In tropical and subtropical countries, the widespread of these diseases
are greater, and it impacts the poorer people more. Since 2014, large epidemic outbreaks
reportedly affected people, claimed lives and disrupted health care services in many
countries: dengue, measles, chikungunya, yellow fever and Zika. Other diseases like
Chikungunya, leishmaniasis and filariasis cause chronic discomfort, lifetime morbidity,
incapacity and occasional stigma.
More than 17% of all infectious diseases account for vector-borne diseases, causing over
700,000 deaths per year. A diverse collection of demographic, environmental as well as social
variables influences the spread of vector-borne diseasesii. Dengue is an evolving infectious
disease spread by vectors. It is the most common Aedes mosquito virus infection. More than
3.9 million individuals, with an approximation of 96 million symptoms and an estimated
40,000 deaths last year, are at risk for developing Dengue in over 129 countries. Dengue virus
(DENV), also known as yellow fever virus, is a member of the flavivirus genus of Flaviviriade
family which also includes yellow fever virus (YFV)iii, West Nile virus (WNV), Japanese
encephalitis virus (JEV) and tick-borne encephalitis virusiv.
Dengue has recently been reclassified by the WHO (World Health Organization) due to issues
when applying the old clinical termsv. The latest recommendations focus on disease incidence
and cases are categorised as dengue, with no symptoms of warning on dengue and severe
cases of it. Severe dengue is characterised as extremely impacted patients with strong plasma
leaking, serious bleeding or organ involvement. The new classification system stresses that
possible signs should be identified early. Latest findings thus show a higher delicacy with the
revised classificationvi. In order to prevent hospitalizations in particular in hyperendemic
environments, early prediction is vital.
While there is no registered dengue vaccine yet, several vaccine potentials have been created.
Live attenuated virus vaccines, live chemistry, inactivated virus, live recombinant, DNA, or
sub-unit vaccines are all usedvii. Live viral vaccinations were carried out in clinical trials, but
issues occured, such as uneven immunogenicity among four tetravalent formulations and
viral involvement among the four serotypes. For safety purposes, non-viral vaccines were also
suggested and developed. Sub-unit vaccinations primarily based on the Eprotein or its
components are used. Live attenuated virus vaccines include susceptible viruses that can
cause structural and nonstructural protein adaptive immune reactionsviii. Replication of the
viruses that are attenuated should be limited enough to deter pathological results. A Live
attenuated virus vaccine is the 17Dstrain of YFV, one of the most effective cases. The quest
for a dengue vaccine which was also promising has, sadly, proved to be less difficult ix.
In conclusion, essential elements in the production of dengue vaccines include common
factors such as immunogenicity, reactogenicity and protective effectiveness. Ideally these
dimensions should be tempered by cost and stability considerations.
(500 words)
Referencing
i
CIESIN (Center for International Earth Science Information Network). Changes in the incidence of vector-borne
diseases attributable to climate change. 2007. http://www.ciesin.columbia.edu/TG/HH/veclev2.html.
ii
il L, Lopez C, Blanco A, Lazo L, Martin J, Valdes I, Romero Y, Figueroa Y,Guillen G, Hermida L:The cellular immune
response plays an importantrole in protecting against dengue virus in the mouse encephalitismodel.Viral
Immunol2009,22:23–30.
iii
Barrett AD, Monath TP, Barban V, Niedrig M, Teuwen DE:17D yellow fever vaccines: new insights. A report of
a workshop held during the World Congress on medicine and health in the tropics, Marseille, France, Monday
12 September 2005.Vaccine2007,25:2758–2765.
iv
Clyde K, Kyle JL, Harris E:Recent advances in deciphering viral and host determinants of dengue virus replication
and pathogenesis. J Virol 2006, 80:11418–11431.
v
WHO (World Health Organization). Vector-borne diseases. Geneva: World Health Organization; 2020.
https://www.who.int/en/news-room/fact-sheets/detail/vector-borne-diseases
vi
Blaney JE Jr, Sathe NS, Hanson CT, Firestone CY, Murphy BR, Whitehead SS:Vaccine candidates for dengue virus
type 1 (DEN1) generated by replacement of the structural genes of rDEN4 and rDEN4Delta30 with those of
DEN1.Virol J2007,4:23.
vii
Sun W, Edelman R, Kanesa-Thasan N, Eckels KH, Putnak JR, King AD, HoungHS, Tang D, Scherer JM, Hoke CH
Jr, Innis BL:Vaccination of human volunteers with monovalent and tetravalent live-attenuated denguevaccine
candidates.Am J Trop Med Hyg2003,69:24–31.
viii
Sabchareon A, Lang J, Chanthavanich P, Yoksan S, Forrat R, Attanath P,Sirivichayakul C, Pengsaa K, Pojjaroen-
Anant C, Chokejindachai W,et al:Safety and immunogenicity of tetravalent live-attenuated denguevaccines in
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ix
Durbin AP, Kirkpatrick BD, Pierce KK, Schmidt AC, Whitehead SS:Development and clinical evaluation of
multiple investigational monovalent DENV vaccines to identify components for inclusion in alive attenuated
tetravalent DENV vaccine.Vaccine2011,29:7242–7250.