Future issues of vector-borne disease notes by SANJU SAH.pptx

Future issues of vector-borne diseases are likely to escalate due to climate change, urbanization, and increased global travel, enhancing the spread and survival of vectors. Emerging pathogens and insecticide resistance further complicate control efforts. Proactive strategies in surveillance, research, and global cooperation are essential to mitigate these growing threats

1. Future issues of vector-borne diseases Prepared by- SANJU SAH St. Xavier’s College, Maitighar , Kathmandu

2. Introduction Vector-borne diseases (VBDs) are human illness caused by parasites, viruses and bacteria that are transmitted by mosquitos, sandflies, triatomine bugs, black flies, ticks, tsetse flies, mites, snail and lice. It accounts for more than 17% of all infectious diseases causing more than 7000000 deaths annually. VBDs are Malaria, Dengue, Schistosomiasis, human African trypanosomiasis, leishmaniasis, Chagas disease, yellow fever, Japanese encephalitis and Onchocorciasis globally.

3. The burden of these diseases is highest in tropical and subtropical areas and they disproportionately affect the poorest population. Since 2014, major outbreaks of dengue, malaria, chikungunya yellow fever and Zika have afflicted populations, claimed lives and overwhelmed health systems in many countries. Many of these diseases are preventable through informed protective measures.

4. M ajor VBDs in Nepal Malaria Dengue fever Scrub typhus Japanese encephalities Visceral leishmaniasis Lymphatic filariasis

5. Malaria Malaria is still a priority public health problem of Nepal where about 84% of the population are at risk and 4% are at high risk.  One million people live in areas with a reported incidence of more than one case per 1,000 population per year. However, the scale of preventive interventions appears to have been limited in Nepal. In recent years, malaria control activities have been carried out in 65 districts at risk out of 75 administrative districts .

6. IN 2010, these 65 districts were further categorized for malaria control programme interventions. Based on the annual parasite incidence (API), there were 13 high-risk districts (API ≥1), 18 moderate-risk districts (API = 0.5-1), 34 low-risk districts (API = 0-0.5) and ten no-risk districts (API = 0).

7.  The Global Fund to fight AIDS, tuberculosis and malaria (GFATM) started supporting a malaria control programme in high-priority, malaria-risk districts in Nepal in April 2004 . Since 2011, the GFATM has scaled up its support for the malaria control programme in 18 additional moderate-risk districts .

8. The GFATM support is utilized for rapid diagnostic test (RDT) kits, artemisinin combination therapy (ACT), long-lasting insecticidal nets (LLINs), and information, education and communication/ behaviour change communication (IEC/BCC) for LLIN use . After the introduction of these interventions, the number of confirmed malaria cases in Nepal declined substantially.

9. Malarial in Nepal

10. Dengue fever Dengue is an acute infectious disease caused by dengue viruses and transmitted by the Aedes species of mosquito. The rapid global spread of the dengue virus into new areas has begun to attract more research attention. A series of dengue fever outbreaks in several districts of Nepal has been recently observed. The evidence of all four serotypes (DEN – 1 - 4) could be a consequence of a sudden resurgence of a more severe dengue disease in Nepal. Health care providers need to become familiar with the disease to prevent or control the possibility of future outbreaks .

11. Contd… Until 2006, DF was reported in nine districts, while Ae. aegypti, the primary vector of DENV transmission has been found in 5 districts. During the 2010 outbreaks, DF cases were reported from 24 districts , indicating that rapid geographical expansion is occurring within the country . This observation raises a serious concern about its potentiality to spread to other parts of the Country. Dengue infection is relatively new disease in Nepal hence much is not known about its frequency among the local population.

12. T he role of Ae. albopictus in the transmission of DENV in Nepal is not very well documented, since its role has been shown to be relatively minor, compared to Ae. aegypti, in DENV transmission elsewhere. So far, no accurate, reliable and timely information on DENV infection is available. To accomplish these requirements, a comprehensive nationwide integrated epidemiological-entomological surveillance needs to be put high on the priority, and must be incorporated into the national health policy. The time has come to recognize it as a major public health problem. Therefore, the state and stakeholders should come up with a campaign to promote public awareness so as to prevent or respond to possible outbreaks of DENV in the future.

13. Scrub typhus Scrub typhus  is a mite-borne disease caused by Orientia tsutsugamushi (formerly Rickettsia tsutsugamushi). Symptoms are fever, a primary lesion, a macular rash, and lymphadenopathy. Scrub typhus is a rickettsial disease, reported from many Asian countries including Nepal. The presence of scrub typhus in Nepal was officially confirmed in 2015. In 2015, a total of 101 cases were reported from 16 districts . Out of them, 8 cases died, accounting about 8% of case fatality rate. Nepal again suffered from scrub typhus outbreak in 2016 with more than 800 reported cases and 14 deaths . A total of 47 districts were affected by the epidemic.

14. Contd…  Although the disease is endemic in our country, it is grossly underdiagnosed owing to non-specific clinical presentation and lack of diagnostic facilities . It is thus suggested that high index of suspicion should be maintained for cases presenting with febrile illness . Infection with Scrub typhus was found high and this calls for an urgent need to introduce vaccine against Scrub typhus. 

15.  In the present context of Nepal , the use of doxycycline as an empirical agent for undifferentiated febrile illness is justifiable .  However , it is highlighted that suspected and proven doxycycline-resistant scrub typhus  and strains with reduced clinical susceptibility to doxycycline , as compared with other drugs such as rifampicin , have been well documented.