Why is Aedes so good at being a vector?

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Seeing the Zika virus epidemic in South America it is hard to believe that just 50 years ago the Aedes mosquitoes that spread it  and several other tropical diseases were nearly eliminated in that region. Ever since then it seems we have been going backwards in mosquito control. Aedes aegypti seems to be adapted to city life and is thriving in the rapidly growing mega cities of South America.

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How effective are current measures for protecting horses from African Horse Sickness?

By Miroslav Djuric, DVM, CAB International, Wallingford, UK.

African horse sickness is a serious and often fatal disease of horses, mules and donkeys caused by African horse sickness virus (AHSV), of the genus Orbivirus in the family Reoviridae. It can also affect zebras, camels and dogs, but not humans. Zebras and donkeys rarely develop serious disease.

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The virus is spread by infected insects (mosquitoes and biting midges) and causes fever, heart and respiratory problems in affected animals.  Death is common and can occur suddenly.

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Dengue situation in a Southern Indian state (Andhra Pradesh) – Gaps and opportunities in Community Awareness

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Photo: WHO/J.Gusmao. Used tyes are an ideal habitat and breeding ground for mosquitoes carrying dengue

Our guestblogger is Dr Manoj Aravind, a researcher in Community Medicine, Hyderabad, India and member of the health information forum HIFA2015.  Under World Health Day 2014's theme "Small bite, big threat" with its goal of better protection against vector-borne diseases, he describes the case for community action against dengue in his home state of Andras Pradesh. He can be contacted directly by email: aravindbm@gmail.com

Dengue is the fastest growing vector-borne disease (VBD) worldwide, and Andhra Pradesh (a Southern Indian state) is no exception. Here, the cases of dengue reported have been steadily rising from 313 in 2008 to 2299 in 2012. The issue of missed cases due to the partial reporting of dengue positive cases by private hospitals and clinics, which are the most commonly used heathcare facilities in our state, make us sceptical of the true burden of this potentially deadly disease. Having a tropical climate, with increasing urbanization, mostly unplanned, and not much “people participation” in health issues increases our cause for concern.1

Mosquitoes are the most common insects today that city dwellers encounter and one species, Aedes aegypti,  are the vector for dengue, transmitting the disease to people via their bite: they are day-biting and breed in clean water collected inside and around houses, especially in urban areas.2 As dengue does not have vaccine or cure, the emphasis is on prevention. The World Health Organization is using this year's World Health Day to build awareness about VBDs and reinforce the need for community empowerment in terms of protecting against these small creatures which are a huge threat to the health of the entire community.3 Andhra Pradesh’s state health machinery is using this opportunity to reach out & empower different stakeholders with effective communication and information.

Awareness of people regarding dengue

When there is no biological vaccine for a disease, knowledge of how this disease spreads and how to prevent this becomes very important. It may then be apt to say that health education leading to healthy behaviours acts as a social vaccine.

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The 2014 World Health Day focuses on Vector-Borne diseases

WHO_SHollyman_woman&net Tanzania
Image : WHO/S.Hollyman

From guest blogger: Dr Joseph Ana, Editor-in-Chief, BMJ West Africa and member of the steering group of the health information forum HIFA2015 . He can be contacted directly by email: jneana@yahoo.co.uk

It
is right that the World Health Organisation (WHO) should focus on vector borne diseases this year, and by so doing raise awareness, disseminate information and improve, hopefully prompt, more effort at preventing and managing the myriad diseases that vectors inflict on man, especially in the Tropics and Sub-tropics.

Whether it is from the arthropod invertebrates of mosquitoes (malaria, dengue, yellow fever), sandflies (skin and systemic Leishmaniasis), bugs (Louse-borne typhus), and ticks (Lyme disease); or from crabs/crayfish (paragonimiasis) and snails (schistosomiasis), or from vertebrate vectors like bats (rabies, ebola disease), vectors are responsible for a large chunk of the disease burden thathealth systems across the globe have to deal with, particularly in the poorer tropical and sub-tropical parts. There is a popular saying that the Traditional African way of cooking all meals ‘well done’ and avoiding eating raw sea food (crabs and crayfish) has helped to keep to a minimum diseases from these vectors.  Snail is also a very popular delicacy which is served ‘well cooked’ for the same reason.

The World has experienced increased incidence of arthropod borne disease since the 1970s 1,2,4, especially in the regions with the weakest health systems such as the tropics and subtropics. But for several reasons the temperate parts of the globe are also affected, which is why it is apt and timely that the WHO is focusing world attention on vector-borne diseases this year (2014). The reasons that account for the global nature of the menace of vector-borne diseases include increased travel by all modes; poor public health practice and infrastructure; massive population increases with urbanization and slums; poor surveillance and control measures; changing agricultural practices and deforestation; lack of effective drug and insecticide control leading to resistant vectors and pathogens; inadequate political will;  etc.

The World should recognize, support and assist those countries where good public health practice has shown that control (and elimination) of vectors leads to decrease in vector borne diseases and help to extend such best practices to regions that are lagging behind. A good example of such best practice in the tropics is Cross River State of Nigeria which has a deliberate Public Health Policy of making its major urban areas ‘Clean and Green’ beginning from Calabar, the state capital.

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Malaria can climb mountains when temperatures rise

A.gambiae.1665p_loresJim Gathanycdc

A study in Science  by Siraj and colleagues this week showed malaria occurs at higher altitudes in warmer years. Their modelling predicts that a one degree Celsius temperature rise in the Ethiopian highlands could lead to 2.8 million more cases in children each year in current malaria areas and over 400,000 cases in new areas. The finding is early warning of what could happen to malaria spread as the world warms if no action is taken.

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Climate change – will it affect spread of vector borne diseases?

Climate change is going to mean mosquito-borne diseases
spread north out of the tropics right? That seems to be the story the news media are giving us. But it is really the case? Do we really need to start thinking about buying bednets to protect against mozzy bites?




Aedes mosquito(CDC)As editor of Global Health database I was invited to the ISNTD Bites
seminar in London, at the Natural History Museum where the issue was hotly debated. The session on climate change and disease vectors showed that
while biology of disease vectors like mosquitoes and sandflies is affected by temperature there are several other
factors that influence spread of disease vectors and the diseases they carry that may mean they don’t spread in the way straight climate maps predict.
Among these are land use, urbanisation and global trade. In fact, the
entomologists at the seminar were arguing that climate change issues are
distracting researchers from looking more into factors that are having drastic effects on the spread of disease vectors
and disease right now.

 

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