Medical Entomology Assignment: Vector-borne Zoonotic Diseases

This assignment from Jahangirnagar University's Department of Medical Entomology (PHI 209) examines the rising threats of vector-borne zoonotic diseases in Bangladesh. The study explores the concepts of vectors, vector-borne diseases, and zoonotic diseases, highlighting key examples such as Dengue, Chikungunya, Malaria, Nipah Virus, Anthrax, and Avian influenza. It delves into the causes of these diseases, including close contact with livestock, climate change, urbanization, socio-economic factors, and lack of awareness. The assignment emphasizes the public health concerns associated with these diseases, discussing the role of environmental changes and the increasing mortality and morbidity rates. It underscores the importance of vector control and the challenges of insecticide resistance. The work references various studies and reports to support its analysis, providing a comprehensive overview of the issue.

Jahangirnagar University
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Honours _______year Final Examination-20____
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20 - 20
2nd 20
PHI 209
Medical Entomology
Tareq Mahmud
191794
1619
20192949879
19 20
8
10 July

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Vector-borne zoonotic Diseases in Bangladesh: Rising Threats on Public Health
I. Introduction
In the contemporary world, vector-borne zoonotic diseases (VBZD) are not only a global threat
to human life but also to animal welfare. Over the last two decades, many emerging vector-
borne zoonotic diseases have been causing repeated outbreaks in humans in various new
regions (M. A. H. N. A. Khan, 2015).
Bangladesh is one of the top country with widespread zoonotic diseases. The research project
‘The prevalence and effects of zoonotic diseases in humans and animals of Bangladesh’ has
reported that 1415 human pathogens cause 61% of zoonotic diseases, and almost half of the
diseases are considered as emerging re-emerging infectious diseases with a percentage of 13%
and 75% of which are caused by zoonotic pathogens (Samad, 2013) (Islam & Ahmed, 2019).
It is reported that zoonotic bacterial diseases like Tuberculosis, Anthrax, Brucellosis,
salmonellosis, campylobacteriosis, leptospirosis etc. and viral zoonotic diseases such as Avian
influenza, Rabis, Nipa virus infection, Japanese encephalitis, Rotavirus, Dengue fever, malaria
etc. are the most common zoonotic diseases in Bangladesh (Chowdhury et al., 2021). Among
them, Anthrax has spread clinical outbreaks in both humans and cattle In poultry more than
550 outbreaks, and six humans affected case is caused by the highly emerge pathogens H5N1,
avain influenza virus. It has been spread badly in 51 out of 64 districts in Bangladesh during
2007 (Samad, 2013). Rabies has infected 100,000 people, of which 2000 have died in 2009
(Samad, 2013). More than 300 human cases were reported since the first outbreak in 2001 by
another crucial emerging pathogen Nipah Virus (Islam & Ahmed, 2019). Many other factors
are responsible for the high prevalence of zoonotic diseases in Bangladesh. Emerging, re-
emerging and neglected zoonotic diseases have become more widespread in Bangladesh and
pose a huge public health concern.
II. Concept of Vector, Vector-Borne Disease and Zoonotic Disease
Vector-borne diseases have been present for a long time, but they threaten human life and
become a major global concern during the last several decades.
Vector
Vector is characterized as an arthropod or any living transporter that moves an irresistible agent
to a vulnerable person. Vector can transmit infectious pathogens both human to human or

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human to animal (WHO, 2020). Mosquitos, flies, fleas, lice, biting flies, bugs, ticks, mites,
helminths etc., are the common vector for transmitting vector-borne diseases. Many of these
are bloodsucker which ingests disease-producing microorganisms during a blood meal from an
infected host (human or animal) and later inject it into a new host during their subsequent blood
meal. Mosquitoes and ticks are the best common vector for disease transmission.
Vector-Borne Disease
Vector-borne diseases are infections that are primarily or exclusively transmitted throw an
invertebrate, generally insects. Some pathogens undergo an obligate stage of their life cycle
inside the vector. Others use the vector-only for transport and inoculation. Malaria, Dengue,
Chikungunya, Yellow Fever, Zika virus disease, Leishmaniasis etc. are major global vector-
borne diseases identified by World Health Organization.
Zoonotic disease
The diseases and infections, which are naturally transmissible between vertebrate animals and
humans, are zoonotic, and this phenomenon is referred to as zoonosis (M. A. H. N. A. Khan,
2015). Zoonoses may be harmful germs such as bacteria, viral, parasitic agents. A zoonotic
disease is transmitted through the bite of an insect, feces, urine, saliva, blood, semi-cooked
food, milk, aerosol, oral and contact of infected individuals. Rabies, Anthrax, Tularemia, West
Nile virus, Dengue, Leishmaniasis, etc., are vector-borne zoonotic diseases.
III. Major Vector-borne Zoonotic Diseases in Bangladesh
Dengue
Dengue fever is a mosquito-borne viral zoonotic disease. Female mosquitoes transmit it, Aedes
aegypti, Ae albopictus in humans (Mamun et al., 2019). Dengue is also endemic in tropical and
subtropical regions along with Bangladesh. In Bangladesh, Dengue fever was first reported in
1964 as ‘Dhaka fever,’ and in 2000, the Dengue fever outbreak was declared officially (Mamun
et al., 2019) (Samad, 2013) . In the outbreak of 2018, 26 deaths and 129 deaths respectively
have been reported from the Government of Bangladesh officially (Mamun et al., 2019). In
2019, it was reported from the Directorate General of Health Services that 14 people have died
and 19513 people have been affected (Wikipedia, n.d.). Dengue Hemorrhage fever is caused
by Dengue type -3 virus, which is a more severe disease.

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Chikungunya
Chikungunya is a mosquito-borne disease that causes broad dreariness and altogether affects
personal satisfaction. It is a mosquito-borne infection, febrile, and serious arthropathic sickness
brought about by the chikungunya infection (Aedes species). Dengue and chikungunya
infections are both transmitted through a similar mosquito vector and are as often as possible
hard to recognize clinically (Hossain et al., 2018). Muscle torment, joint swelling, cerebral
pain, queasiness, weakness, and rash are the normal indications of this infection and the
sickness spreading framework resembles Dengue. Most victims recuperate totally from
disease, yet joint agony for certain cases can keep going for a couple of months or even a long
time.
Malaria
The position of Bangladesh is 87th among the malaria-endemic countries. It is additionally
endemic in 13 to 64 areas in this country. Malaria is a complicated illness that requires the
continuation of its life cycle through three components – the parasite-vector and the host.
Bangladesh's physical and social climate considers the general endurance of the three vectors
A. philippinesis A. sundacus and A. minimus for malaria parasites, Plasmodium malariae and
Plasmodium falciparum (Paul, 1984). It is sent by tainted mosquitoes. At the point when an
intestinal sickness contaminated host is taken care of by a mosquito, it likewise gets tainted
and can send the parasite to the following individual it nibbles. It might be lethal if not treated.
Moreover, complexities like serious iron deficiency, cerebral intestinal sickness could happen
if infected by malaria.
Nipah Virus
Among the emerging infectious diseases, Nipah virus (NIV) infection is another major zoonotic
disease that infects humans severely and initially manifests symptoms of fever and
encephalitis(inflammation of the brain)(Samad, 2013). Nipah virus infection is a zoonotic viral
infection caused by the Nipah virus originating from a new genus -the Henipavirus. The first
cas of Nipah Virus was reported in 1998 in Nipah village of Malaysia by causing a neurological
and respiratory infection on pig farms in Peninsular (Samad, 2013)(Rahman & Chakraborty,
2012). Primarily Nipah virus is spread by bats and transmitted from one infected human to
another (Rahman & Chakraborty, 2012). In Bangladesh, the recent outbreaks of the Nipa virus
were seen in 2001. Usually, the cause of Nipah virus infection is infected by consuming date

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palm sap contaminated by fruits, bat saliva, or urine (icddrb, n.d.). From 2001-2003, 196 cases
of Nipah encephalitis were identified from 20 districts of Bangladesh clusters, and as isolated
cases, 150 (77%) cases of these deaths have occurred (icddrb, n.d.). An investigation of
‘Human populations in Central and Northwestern Bangladesh’ discovered that 173 human
cases of NiV infection had been recognized in Bangladesh, of which 110 (63.58%) died during
2001-2011 (Samad, 2013). However, to prevent infection, access to bat sap in the date palm
should be reduced, and infected family members and friends should be kept away from contact
with infected saliva.
Anthrax
Anthrax is a zoonotic disease caused by anaerobic, large gram-positive rod -Bacillus antracis
bacteria and affect human and animal (Siddiqui et al., 2012) (Galante et al., 2021). It is recorded
that the tropical and subtropical area is the highest prevalence region of Anthrax (Samad,
2013). Anthrax is endemic in Bangladesh and was reported in Bangladesh from 1980 to 1984
(Siddiqui et al., 2012).In the summer and monsoon season (April to October), more than 25
outbreaks are identified in humans and cattle, and more than 650 human cases from 15 districts
are recorded during 2009-2012 in Bangladesh. Moreover, because of this result, the
Government of Bangladesh declared ’a red alert’ due to the sudden outbreak (Samad, 2013)
(Siddiqui et al., 2012).The outbreak was caused by the slaughter of infected cattle and the
selling or eating of contaminated meat. The outbreak emerged severely in six districts, Pabna,
Sirajganj, Rajshahi, Kushtia, Tangail, and Bogura. Increasing public education and awareness
about Anthrax, an organized and routine vaccination of cattle, quarantine of all imported and
slaughtered cattle, proper disposal of carcasses and contaminated materials, meat inspection by
the Vets, and meat sale the licensed meat vendors would certainly help to control Anthrax in
Bangladesh.
Avian influenza
Another important viral vector-borne zoonotic infection is avian influenza caused by the highly
pathogenic avian influenza (HPAI) virus and affects both birds and mammals. On March 27,
2007, the declaration of AI outbreak which H5N1 transmitted, was announced officially first
in Bangladesh. After this period, official publications have shown that the virus has spread to
51 of the 644 districts as well as caused more than 460 outbreaks with killing more than two
million birds. A study on 311 asymptomatic poultry workers in 2012-2013 found that
nasopharyngeal swabs contain 4.5% and arm swabs contain 18.5% detectable avian influenza

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viruses (AIV)RNA (Rimi et al., 2019). Though the effective human-to-human transmission of
the HPAI virus has not been precisely verified, the high population density and the results of
close human-animal contact in Bangladesh are responsible for the outbreak. Poor management
systems, as well as breaches in biosecurity practices, appeared to have a significant role in the
spread of HPAI. But Bangladesh was considered free from human infection up to May 21,
2008. The authorities of Bangladesh declared one human case infected by the avian influenza
virus on May 22, 2008. The case confirmed by the Center for Disease Control and Prevention
(CDC) in Atlanta, USA, and with this suspected case, Bangladesh placed in the 15th position
of the world to report human infection with HPAI H5N (Alam et al., 2010).
IV. Causes of Zoonotic Diseases in Bangladesh
Vector-borne emergence is commonly driven by changes in anthropogenic factors, ecological
and environmental factors.
1.In Bangladesh, the main reason for becoming vector-borne zoonotic diseases is very close
contact with their domestic livestock and poultry. Most of these domestics animals act as
reservoirs and carriers to spread zoonotic diseases (Chowdhury et al., 2021).
2.Climate change has a great impact on the spread of the zoonotic pathogen. As in other
vulnerable countries, in Bangladesh, various types of natural calamities such as cyclones,
frequent flooding, soil erosion, destruction of biodiversity etc., play a major role in the
emergence of zoonotic diseases through contaminated water and food (Chowdhury et al.,
2021).
3.Other anthropogenic factors such as urbanization, modernization of agriculture and livestock
farming.
4.Socio-economic factor- Poverty and social inequality.
5.Human habitat factor -lack of awareness about disease control program, lack of hygienic
management knowledge, food habits etc., also responsible for transmitting VBZD in humans.

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V. Why Vector-borne Zoonotic Diseases are great concern of Public Health
Figure-1: Role of vector in different areas regarding vector borne diseases
Environmental changes in Bangladesh like moistness, precipitation, and inordinate warmth
assist with expanding the quantity of sickness, insect, bug, micro-organisms that significantly
affect general well-being and public health. A few illnesses are reappearing like Malaria,
Dengue, Chikungunya, Kala-azar etc. As a result, the mortality and morbidity rates are
increasing for vector conceived zoonosis infection. Throughout the long term, vector control
has been a significant part of diminishing the vector-borne disease burden worldwide.
Moreover, it is vigorously dependent on synthetic insecticides as a primary source of food.
Insecticide abuse is responsible for the emergence of resistance, sabotaging the limit of vector
control. The circumstance in Bangladesh is exacerbated by neglected clinical veterinarians and
their augmentation services, low-class individuals with information on zoonotic illnesses in
intimate contact with animals and their items and unhygienic preparing, domesticated animals
and animal products management and commercialization (Samad, 2013).
VI. Conclusion
Vector-borne zoonotic diseases are one of the significant threats to public health. As public
health works in the disease prevention area and the motive of public health is to ensure the
quality of life, vector-borne diseases must be taken into paramount concern. For the effective
prevention strategy, vector control can be a pleasing way. Any massive outbreak of vector-
borne zoonotic disease can occur at any time. So, it is high time public health professionals,
along with policymakers, entomologist should keep their eyes on the spreading of vector-borne

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zoonotic diseases. The motion, possibility of an epidemic in the near future should be assessed
with great importance.
VII. References
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Avian Influenza in Bangladesh: A review. World’s Poultry Science Journal, 66(3), 455–
464. https://doi.org/10.1017/S004393391000053X
Chowdhury, S., Aleem, M. A., Khan, M. S. I., Hossain, M. E., Ghosh, S., & Rahman, M. Z.
(2021). Major zoonotic diseases of public health importance in Bangladesh. In
Veterinary Medicine and Science. Wiley-Blackwell. https://doi.org/10.1002/vms3.465
Galante, D., Manzulli, V., Serrecchia, L., Di Taranto, P., Hugh-Jones, M., Hossain, M. J.,
Rondinone, V., Cipolletta, D., Pace, L., Iatarola, M., Tolve, F., Aceti, A., Poppa, E., &
Fasanella, A. (2021). Investigation on anthrax in bangladesh during the outbreaks of
2011 and definition of the epidemiological correlations. Pathogens, 10(4), 1–10.
https://doi.org/10.3390/pathogens10040481
Hossain, M. S., Hasan, M. M., Islam, M. S., Islam, S., Mozaffor, M., Khan, M. A. S., Ahmed,
N., Akhtar, W., Chowdhury, S., Arafat, S. M. Y., Khaleque, M. A., Khan, Z. J., Dipta,
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Tw3f0pwsyDJI0T2d6Zy0gWGzJRp1jNuSo28d2cY9FvnphS9GgVtiQiE