Control of Zoonotic Diseases

Due to the increase in incidence of zoonotic diseases around the world, efforts have been made and are still being made to control zoonotic diseases.

Since zoonoses involve both humans and animals, efforts to control the diseases require working both with the health and veterinary sector. In as much as these two sectors have to work hand in hand, there is a very important aspect that we also have to consider in order to control these diseases, that is the communities involved.

In the past efforts have been done to control many infectious diseases but unfortunately the most crucial part is always left out until the last minute. Community involvement has always been left out until the last minute when an epidemic has hit or when there is an outbreak. Unfortunately when the disease has been controlled it is all forgotten. There is therefore need for continuity in community involvement to achieve effective control of zoonoses.

With zoonoses being spread from animal to humans through meat, animal products and animal excreta from both wild and domesticated animals, we have to go down to the grass roots, that is the people who live in close proximity with wild and domesticated animals. But who are the people likely to be in close proximity with these animals? These could be farmers, people who live within or in close proximity with rainforests, people working in arbatoires, cattle herders, bush hunters, park rangers, zoo keepers the list is endless. Apart from people who live in close proximity with animals, let us consider also those that consume meat and meat products.

As outlined above apart from experts from the health and veterinary, it is important to involve the community if efforts to control zoonoses have to succeed. How?

Step1:

Through surveillance of food sources in the villages and communities, this includes where they slaughter both their wild and domesticated animals, where they hunt, and most important to test the meat for diseases before it is consumed. In most developing countries, there are communities that are either isolated or have no facilities and or expertise to monitor and or test the meat for diseases. This is an important step as this could be a crucial step in controlling some of the zoonoses.

 Step2:

Knowledge and understanding of their eating and food storage habits, how does the community prepare their meat products, do they eat the meat raw, how do they handle the meat after slaughter?

This step is crucial in understanding where the source of the disease as well as it can be used as a screening process for what could be the zoonoses that can survive in the various methods of food processing used in the community and or village. For example if they consume the meat raw, then we start looking at zoonoses that are spread through animal blood, those that survive as cysts in the animal flesh, those present in the bowels and animal excreta and so on.

Step 3:

Sanitation, which includes disposal of animal remains, proximity of people to their livestock, management of livestock and exposure to animal excreta (in case of leptospirosis) is also another important factor to consider if we can control zoonoses. This point puts emphasis on the fact that an infected animal carcass or any animal remains are still a source of zoonoses. Poor disposal can lead to spread of diseases.

From these three steps outlined it is crucial to have community involvement much earlier even before the onslaught of the diseases. If through surveillance, there is knowledge of the possible zoonoses that could affect a particular community, it is importantl to alert the community before hand and offer the necessary training and advice to avoid the spread of the diseases. Knowledge of day to day habits of a community can be a good start in communicating to the community of the lurking dangers with regard to animals and their products. Community leaders have a good connection as regards communication and execution of instructions within their communities. These leaders are therefore an important link between health/veterinary experts and the entire community. It is important to understand hierarchies within the communities as this is a crucial aspect in communicating with communities especially in rural areas.

Zoonoses and Man; Where can we find zoonotic diseases?

Human beings have always lived in close proximity with animals for centuries. Animals have been used as beasts of burdens on farms and households as well as a source of meat and animal products such as milk, eggs, meat and leather. Animal excreta has been used as a source of manure and biogas.

In as much as animals have always provided for man, they have also been a source of some of mans’ worst diseases some of which are curable and others incurable.

The diseases that are carried by animals and are passed on to humans are called zoonosis(es). Some of the modern diseases that started as zoonoses include:

·         Measles

·         Smallpox

·         Influenza

·         HIV

·         Diptheria

In my previous entry, I outlined zoonotic diseases by their causative agents and you will notice that the 5 diseases I have mentioned above including SARS, rabies, echirococcosis, taeniasis, brucellosis and trematodisis, are the major diseases that are of focus as public health threats.  But there are many more zoonotic diseases the world is not paying attention to and yet they are causing death  and becoming a public health issue. As such most zoonotic diseases are also known as neglected tropical diseases (NTDs).

Where are these zoonotic diseases found?

From the name neglected tropical diseases one could have a clue that these diseases mostly occur in the tropics. They are commonly found in Latin America, South East Asia and part of the Congo basin.

Below is the list of countries where NTDs are a major problem;

Americas and Latin America	South East Asia	Africa
Mexico	India	Cameroon
Colombia	Vietnam	Tanzania
Ecuador	Laos	Congo- DRC
Peru	Bangladesh	Uganda
Bolivia	Cambodia
Peru	Thailand
Brazil	Malaysia
Venenzuela
USA

Outbreaks of zoonotic diseases have occurred in different parts of the world but the countries mentioned above have experienced some of the major outbreaks or have frequent outbreaks of zoonoses.

It is interesting to note that the countries that are mentioned in the table above have something in common, close proximity to rainforests. Is there any association between zoonoses and proximity to rainforests? From the map (

www.healthmap.org/predict/) I noticed that most of the zoonotic oubreaks occured in countries where there is a rainforest. In Africa, the Congo basin host the second largest rainforest in the world, the Congo rainforest, which encompasses, Cameroon, Congo-DRC and Equatorial guinea. While in Latin America, the countries affected by zoonoses host the worlds largest rainforest, the Amazon rainforest. In South East Asia, Malaysia and Indonesia also have some raiforests.

 

One important thing to note is that the rainforests of Africa, South East Asia and its associated archipelagos, and tropical America they match in their animal and plant diversity.

 

So what are the animals that are shared bewteen these rainforests which could be major carriers of zoonotic diseases?

 

Below is a list of animals associated with zoonotic diseases, I beleive one will be able to pack out some animals that are associated with rainforests.

 

Higher Mammals	Other mammals	Birds	Others
Cattle	Bats	Geese	Ticks
Chimpanzees	Hamsters	Chickens	Snails
Humans	Hyraxes		Mosquitoes
Gorillas	Oppossum		Fleas
Monkeys	Rabbits and hares		Flies
Dogs	Raccoons		Lice
Cats	Rats		Assasin bugs
Horses
Pigs
Sheep
Sloth
Wolves

In my next entry I will discuss further some of the major zoonotic outbreaks in the world and what is being done to control this emerging public health issue.

References

www.healthmap.org/predict/

 

Zoonoses

For the past month I have been writing on various infectious diseases that are affecting our world today.

In my entry today I will continue on our topic of infectious diseases and we are going to look at what are known as zoonoses.

First of all let us start by defining the word Zoonosis (plural- Zoonoses). Zoonosis is any disease or infection that is naturally transmissible from vertebrate animals to humans. Zoonoses are diseases of interest to humans  as humans have for centuries interacted with animals both wild and domesticated. Zoonoses can be transmitted through animal excreta, urine, and animal products.

Over 200 zoonoses have been described so far and atleast 61% of all human pathogens are zoonotic.  The big question is still what causes zoonoses?

Zoonoses are caused by various agents including:

·         Bacteria

·         Parasites

·         Fungi

·         Viruses

·         Unconventional agents

Let us break down some of the zoonotic diseases by their causative agents.

1.    Zoonoses caused by Bacteria

·         Salmonellosis

·         Campylobacteriosis

·         Anthrax

·         Brucellosis

·         Leptospirosis

·         Plague

·         Q-fever

·         Shigellosis

·         Tularaenia

2.    Zoonoses caused by Parasites

·         Cysticercosis/Taeniasis

·         Trematodosis

·         Echinococcosis

·         Toxoplasmosis

·         Trichinellosis

3.    Zoonoses caused by viruses

·         Rabies

·         Avian flu (bird flu) H5N1

·         Crimean- Congo hemorrhagic fever

·         Ebola

·         Rift valley fever

4.    Unconventional agents

·         These are agents that are yet to be defined for example the agent that causes spongiform encephalopathy the same variant that causes variant Cruetzfeldt-Jakob disease (vCJD).

In the coming weeks I will be looking at how zoonoses have affected communities, the efforts that have been put forward to overcome these zoonoses and the way forward.