15/07/2023
One Health Issues
(4) Vector-borne Diseases
Vector-borne diseases (VBDs) are carried by living beings called vectors: mosquitoes, ticks, fleas 🦟. They account for over 17% of infectious human diseases, some of which can also infect animals.
Vector-borne diseases account for 17% of the estimated global burden of all infectious diseases, and transmission has become increasingly ubiquitous with the largest risk zones in Africa, Asia, and the Americas. As a major cause of morbidity and mortality in humans and livestock in pastoral and mixed farming communities in developing countries, VBDs reinforce the vicious cycle of poverty by limiting productivity and the ability to produce food or earn income to purchase food or medical services.
Due to the influence of human activity on disease incidence and the direct and indirect impact on human health and livelihoods, VBDs are highly suited to ‘one health’ concept for combating infectious diseases. Increased human mobility, population growth, trade, and climate change constitute major risk factors for geographic expansion to new areas.
Human activities like construction of dams and irrigation schemes can enhance food and energy demands of the developing countries nevertheless they have been concerned for steady transmission amplification or introduction of new vector-borne infectious diseases.
Vectors are frequently arthropods, such as mosquitoes, ticks, flies, fleas and lice.
Vectors can transmit infectious diseases either actively or passively:
🦟Biological vectors, such as mosquitoes and ticks may carry pathogens that can multiply within their bodies and be delivered to new hosts, usually by biting.
🪰Mechanical vectors, such as flies can pick up infectious agents on the outside of their bodies and transmit them through physical contact.
How do vectors transmit pathogens?
With vertebrate hosts, vectors become infected when they acquire a pathogen from an infected host during a blood meal, a practice known as haematophagy. The pathogen can then be transmitted to a new host in a variety of different ways, the most common being:
1. injection of saliva during a new bite: the viruses transmitted by certain mosquitoes or the parasite responsible for sleeping sickness (transmitted by the tsetse fly) are injected during a bite;
2. faeces: for example, the parasite responsible for Chagas disease is transmitted by the faeces of an infected triatomine bug;
3. regurgitation: the bacterium responsible for the plague (Yersinia pestis) is transmitted by fleas during regurgitation;
4. active migration of the parasite during the bite (filariasis).
Read more at:
The case for a ‘one health’ approach to combating vector-borne diseases
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4450247/
European Food Safety Authority: Vector-borne diseases
https://www.efsa.europa.eu/en/topics/topic/vector-borne-diseases
Emerging and Re-emerging Vector-Borne Infectious Diseases and the Challenges for Control: A Review
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8524040/
anses (France): Vectors and the diseases they transmit
https://www.anses.fr/en/content/vectors-and-diseases-they-transmit