Tag: ntd

The First Non-infectious NTD

The World Health Organization has a list of diseases, called neglected tropical diseases (NTDs), that they are working to control through widespread public health policies. These are diseases that are prevalent in tropical and sub-tropical climates in which “Populations living in poverty, without adequate sanitation and in close contact with infectious vectors and domestic animals and livestock are those worst affected.”[1] One of the more recent diseases, as well as the first non-infectious disease to be added to the list, is snake envenomation.

Why was “snake-bite” added to the NTD list? Most people don’t often think of it when someone mentions ‘disease’. There are four criteria that must be fulfilled to be placed on the World Health Organization’s neglected tropical disease list.[2]

  1. Significant burden of the disease; many people are affected, and many die.
  2. Majority of cases occur in tropical or sub-tropical geographical areas, and impacts the poor in particular.
  3. The impact of the disease can be mitigated through treatment and prevention.
  4. The cost of researching and implementing prevention strategies is ultimately cheaper than the disease’s impact.

Snakebites meet all four criterion. 250 species of dangerously venomous snakes are present in 160 countries around the world,[3] and snake-bite encounters occur around 5.5 million times every year. Of these, WHO estimates that 400,000 victims suffer permanent disabilities, and up to 138,000 do not survive.[4] The majority of these bites take place in sub-Saharan Africa, South Asia and South-East Asia where the majority of the world’s population is concentrated. The groups at the highest risk of potentially-fatal bites include poor rural dwellers, agricultural workers (including farmers, herders, fishermen, and hunters), children, pregnant women, and any with restricted or no access to healthcare.[5]

WHO believes that their estimates for the number of snakebites that occur is drastically lower than the actual number of cases, because around half the victims in poor areas will make use of traditional medicines rather than seeking more advanced medical attention. Though this could be due to cultural reasons in some cases, in many others it is because the victims do not have access to proper care.[6]

Antivenom is one of the most common and effective methods of dealing with snake envenomation, and it can be relatively cheap to produce. However, the quality and availability of antivenom can be very limited, especially in poor areas. Inadequate product safety and efficacy, lack of properly trained health personnel, absence of neutralization specifications, and local superstition surrounding snakebites, all contribute to inaccessibility of medical care. Many companies attempting to produce good quality antivenom are driven out by lower quality products sold at cheaper prices.[7]

https://www.who.int/snakebites/antivenoms/Cycle_of_antivenom_market_decline.pdf?ua=1

To effectively be able to provide medical care access around the world, it is not enough to produce vials of antivenom. Like with the other NTDs, a multi-pronged One Health approach will be the most effective strategy. The antivenom must be of tested and guaranteed quality, ensuring effectiveness. Public education programs must also be implemented, to encourage locals to seek proper medical attention after a snakebite, as well as direct them to trusted sources for their antivenom. Protective footwear to protect from bites, netting or other barriers to keep snakes out of homes, keeping paths and other areas clear of refuse piles to reduce hiding places, and cutting grass short to make snakes more visible, are all effective environmental strategies to prevent snakebites.[8]

[1] https://www.who.int/neglected_diseases/diseases/en/

[2] https://www.who.int/snakebites/snakebites_FAQ/en/index1.html

[3] https://www.who.int/snakebites/disease/en/

[4] https://www.who.int/neglected_diseases/news/Snakebite-envenoming-mandate-global-action/en/

[5] https://www.who.int/snakebites/epidemiology/en/

[6] Ibid.

[7] https://www.who.int/snakebites/antivenoms/en/

[8] https://www.who.int/snakebites/snakebites_FAQ/en/index6.html

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How’s About the Epidemiological Triad?

An epidemiological triad is a tool used by One Health professionals to not only identify and categorize a health issue, but to also develop a control plan.

This is a general example of an epidemiological triad.

https://qph.fs.quoracdn.net/main-qimg-6622d9b9a55f6372dbd3e0f293d06676

It has three corners: host, agent and environment.

The ‘agent’ stands for whatever it is that causes the disease. This can be a virus, a bacterium, a toxin, etc. We need to make a distinction between the disease itself and the agent that causes it. The flu disease consists of the common flu symptoms, but the agent that causes the disease is the Influenza virus. Just because someone is infected by the Influenza virus, doesn’t necessarily mean that they will get the flu disease; for example, if they are healthy and have gotten a flu shot, they will be less likely to get sick. In the ‘agent’ section of the triangle they list all the features of the agent that may cause disease.

The ‘host’ is whatever the agent can cause disease in. Some species are resistant or immune to certain agents, and will not come down with the disease even if they are infected. Some animals are naturally resistant to disease by the agent unless certain conditions are fulfilled; for example, if the animal is young, old, stressed, starved, or otherwise weakened. In this section of the triangle they list all the conditions that could predispose a possible host to contracting the disease when infected by the agent.

The ‘environment’ section stands for the environmental conditions that could increase chances of a host coming into contact with the agent, and make the host more susceptible to contracting the disease. In this instance, if the geographical area is favorable to the agent’s survival, if the host is constantly in close contact with infected individuals, has limited access to medicine or sanitation, or other conditions that may make disease more likely.

Here’s an example of an epidemiological triad for an actual disease, Scabies:

This disease is caused by the agent Sarcoptes scabei, a microscopic mite. The unique thing about this agent is that cases of disease are very uncommon in developed countries where most inhabitants have access to healthcare, and are not overcrowded. In developing countries, however, it is one of the most common causes of skin diseases, and is most prevalent in tropical areas where the mites survive best.[1] For this reason, scabies is considered a neglected tropical disease: a disease which disproportionately affects “populations living in poverty, without adequate sanitation, and in close contact with infectious vectors.” [2] Young children and the elderly are particularly susceptible to contracting scabies, as well as secondary complications.

A triad like this is used to find possible control points in the disease cycle. The agent could be controlled by administering scabicide, a medicine that kills the mite. Prevalence of the disease could be lessened by controlling the disease in the stray dogs that can transmit the mite to people.

The triad could also be used to identify areas and situations at high risk for scabies outbreaks, and allow surveillance and preparations to react in case one actually takes place. Right now the World Health Organization recommends mass administration of scabicidal drugs as the most feasible and effective method of controlling the scabies disease.

The epidemiological triad is a good example of what One Health is about: taking into account the whole picture of what leads to disease, by listing and investigating all the factors. Looking at ways to intercept and stop the disease cycle, and not just focusing on treating those who are already infected. Working for the improved health of all people, as well as animals and the environments they live in.

[1] https://www.who.int/neglected_diseases/diseases/scabies/en/

[2] https://www.who.int/neglected_diseases/diseases/en/