Vector-Borne Diseases

18 December 2021


A vector is any agent usually arthropods which carries and transmits an infectious agent ( bacteria, viruses, protozoa, or helminths) into another living organism. Many of these vectors are bloodsucking insects, which ingest disease-producing microorganisms during a blood meal from an infected host (human or animal) and later transmit it into a new host after the pathogen has replicated. Often, once a vector becomes infectious, they are capable of transmitting the pathogen for the rest of their life during each subsequent blood meal. The vector can be biological or mechanical.

Biological vectors

The term biological vector or true vector refers to a vector that not only assists in the transfer of parasites but the parasites undergo development or multiplication in their body as well. Examples of true vectors are

  • Mosquitoes: Malaria, Filariasis, Viral hemorrhagic fevers
  • Sandflies:  kala-azar
  • Tsetse flies: Sleeping sickness
  • Reduviid bug: Chagas disease
  • Ticks: Babesiosis, Ticks-borne relapsing fever

Mechanical vectors

Mechanical vectors assist the transfer of parasites but are not essential in their lifecycle. Examples of mechanical vectors are:

  • Houseflies : Amebiasis, Enteric fever
  • Animals

Animals

Animals can be domestic or wild.

Domestic Animals

  • Cow, e.g. Taenia saginata,  Sarcocystis
  • Pigs: Taenia solium, Trichinella spiralis
  • Dogs: e.g. Echinococcus granulosus
  • Cats: Toxoplasma, Opisthorchis

Wild Animals

  • Wild game animals, e.g. trypanosomiasis
  • Wild felines, e.g. Paragonimus westermani
  • Wild carnivore animals like raccoons, skunks, wolves, foxes and bats carry rabies virus. Domestic mammals cats, cattle, and dogs can also get rabies.
  • Fish, e.g. fish tapworm
  • Molluscs, e.g. liver flukes
  • Copepds , e.g. guinea worm
Aedes aegypti Mosquito
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Vector-borne diseases (VBD) account for more than 17% of all infectious diseases, causing more than 700,000 deaths annually around the world. According to the World Health Organization Global Burden of Disease study in 2004, 7.77% of all human mortality due to infectious diseases was associated with vector-borne diseases such as malaria, dengue fever, Japanese encephalitis, and neglected tropical diseases. The burden of these diseases is highest in tropical and subtropical areas where access to safe drinking water and sanitation system is poor. Mosquitoes cause more death than any other disease vector. Other diseases such as Chikungunya, leishmaniasis, and lymphatic filariasis cause chronic suffering, life-long morbidity, disability, and occasional stigmatization. There is no proper treatment and vaccines available for a few of them only. Many of these VBD are preventable. Control of vectors is often and sometimes the only way to protect humans from these destructive diseases. Disease burden can be reduced or eliminated by improving sanitation, safe drinking water, public education, and awareness.

List of  most important vector- borne diseases globally, infectious agents and  their vectors is as follows:

Mosquito- Borne Diseases

DiseasesVectorsInfectious Agents
MalariaAnopheles
Culex
Protozoa-(Plasmodium-
Falciparum,
P. Malarie, P. Vivax, P. Ovale)
Dengue feverAe. aegypti
Ae Albopticus
Flavivirus
Chikungunya FeverAe. aegypti
Ae. Albopticus
Togaviruses
Zika FeverAedes aegyptiFlavivirus
West Nile fever
(WNF)
culex -modestus West Nile Virus
Rift Valley Fever
(RVF)
Culicine
mosquito
Bunyavirus
Viral encephalitisculexTogaviruses and
Flaviviruses
Bunyaviruses
Elephantiasis,
Lymphedema, hydrocele
Culicine and
Anopheles
mosquito
Wuchereria bancrofti
and Brugia malayi filaria
(Nematodes)
Yellow feverAe. aegyptiFlavivirus
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Fly-borne Diseases

DiseasesVectorsInfectious Agents
Dysenteries, enteric fever,
Amoebiasis, helminth-
infections, anthrax, Tularemia,
cholera, Trachoma,
tropical ulcer
House flies
(Musca and Tabinda)
Enteric bacteria, Entamoeba-
histolytica, bacillus anthracis,
Francisella tularensis-
bacterium, Vibrio cholera,
Chlamydia trachomatis
Leishmaniasis
(Kala-azar
Oriental sore,
Sand fly fever)
Phlebotomine sandfliesLeishmania
( A protozoan)
Onchocerciasis
(river blindness)
Simulium fly
(black fly)
Onchocerca volvulus
(Nematodes )
LoiasisChrysops flyLoa loa filaria
(eye worm)
Sleeping sickness
(African Trypanosomiasis)
Tsetse flyTrypanosoma
Brucei
(A protozoan)

Carrion’s disease
(Bartonellosis)
Phlebotomine sandfliesBartonella bacilliformis
Streptococcal dermititis,
nephritis
Oscind flyStreptococci
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Flea-Borne Diseases

DiseasesVectorsInfectious Agents
Bubonic PlaqueOriental Rat Flea
(Xenopsylla cheopis)
Yersinia pestis
Endemic Typhus Fever
(Murine Typhus)
Oriental Rat Flea
(Xenopsylla cheopis
Rickettsial typhi,
R. felis
TularemiaFlea and Ticks Francisella tularensis
(bacterium)
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Tick -Borne Diseases

DiseasesVectorsInfectious Agents
Rocky Mountain Spotted-
Fever
Ixodid tick
(hard tick)
Rickettsia rickettsii
TularemiaTicks, Fleas and
flies
Francisella tularensis
Human babesiosisIxodid tickBabesia microti,
B. divergens
(protozoa)
Tick paralysis Ixodid Holocyclus
female tick
Holocyclotoxin of
I Holocyclus
female tick
Q (query) feverSoft ticksCoxiella burnettii
Tick-Borne Relapsing Fever
(Borreliosis)
Soft ticks
(Argasid)
and lice
Borrelia recurrentis
Lyme Disease
(Borreliosis)
I ricinus
(deer tick)
I persulcatus
Borrelia burgdorferi,
Borrelia mayonii
Viral fevers and
hemorrhagic fevers
Ixodid tickArboviruses
kyasanur Forest Disease
(KFD)
Haemaphysalis spinigera
tick
kyasanur Forest
Disease virus
Crimean-Congo
Hemorrhagic Fever (CCHF)
Ixodid tickBunyavirus
Tick borne encephalitis (TBE)I ricinus
(deer tick)
Flavivirus
EhrlichiosisAmblyomma americanum
(Lone star tick)
Ehrlichia chaffeensis
(bacterium)
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Louse- Borne Diseases

DiseasesVectorsInfectious Agents
Epidemic Typhus FeverliceRickettsia prowazekii
Louse -Borne Relapsing Feverlice and TicksBorrelia recurrentis
Trench FeverliceRickettsia quintana
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Mites (chiggers) and other vector-borne Disease

DiseasesVectorsInfectious Agents
Mite-Borne or
Scrub Typhus Fever
Trombiculid MitesRickettsia tsutsugamushi
Rickettsial poxLiponyssoides sanguineus
Mite
Rickettsia akari
Chagas Disease
(South American trypanosomiasis)
Triatomine bug
(Reduviid bug or Kissing bug)
Trypanosoma cruzi
( A protozoan)
Guinea worm disease
(Dracunculiasis)

copeode
(cyclops)
Dracunculus medinensis
(Nematodes)
Schistosomiasis
(Bilharziasis)
Fresh water snailsSchistosoma
(Trematodes)
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