How Important to be Aware of Zoonotic Disease?

Over the last century, there has been an alarming increase in the number, frequency, and diversity. Caused by the spillover of pathogens from animal hosts to people, these events may have more than  with the number of new zoonotic diseases infecting people quadrupling over the same period. Today, 60% of emerging infectious diseases in humans are zoonotic.

Zoonotic Disease, a familiar terminology nowadays. It is an infectious disease caused by a pathogenic or agent (a bacterium, virus, fungi, parasite, or viral protein) that has been transmitted from an animal to a human. According to WHO, zoonosis is any disease or infection that is naturally transmissible from vertebrate animals.

Important zoonotic diseases are:

• Zoonotic influenza
• Anthrax
• Salmonellosis
• West Nile virus
• Plague
• Emerging coronaviruses (e.g., severe acute respiratory syndrome and Middle East respiratory syndrome)
• Rabies
• Brucellosis
• Lyme disease

Causes of Zoonotic Disease

In the modern world, Companion animal is a common,  but they can be a source of zoonosis. Zoonoses comprise a large percentage of all newly identified infectious diseases as well as many existing ones. Some diseases, such as HIV, begin as zoonosis but later mutate into human-only strains. Other zoonoses can cause recurring disease outbreaks, such as Ebola virus disease and salmonellosis. Still others, such as the novel coronavirus that causes COVID-19, have the potential to cause global pandemics.

Animals provide many benefits to people. Many people interact with animals in their daily lives, both at home and away from home. Animals provide food, fiber, livelihoods, travel, sport, companionship, and education for people across the globe. Millions of households in the United States have one or more pets. We might come into contact with animals in either urban or rural settings, during travel, while visiting animal exhibits, or while enjoying outdoor activities.

However, animals can sometimes carry harmful germs that can spread to people and cause illness – these are known as zoonotic diseases or zoonoses. Zoonotic diseases are caused by harmful germs like viruses, bacterial, parasites, and fungi. These germs can cause many different types of illnesses in people and animals, ranging from mild to serious illness and even death.

Because of the close connection between people and animals, it’s important to be aware of the common ways people can get infected with germs that can cause zoonotic diseases. 

These can include:

• Animal indirect contact: 

Coming into contact with the saliva, blood, urine, mucous, feces, or other body fluids of an infected animal. Examples include petting or touching animals, and bites or scratches.

• Indirect contact: 

Coming into contact with areas where animals live and roam, or objects or surfaces that have been contaminated with germs. Examples include aquarium tank water, pet habitats, chicken coops, barns, plants, and soil, as well as pet food and water dishes.

•  Vector-borne: 

Being bitten by a tick, or an insect-like a mosquito or a flea.

• Foodborne: 

Each year, 1 in 6 Americans get sick from eating contaminated food. Eating or drinking something unsafe, such as unpasteurized (raw) milk, undercooked meat or eggs, or raw fruits and vegetables that are contaminated with feces from an infected animal. Contaminated food can cause illness in people and animals, including pets.

• Waterborne: 

Drinking or coming in contact with water that has been contaminated with feces from an infected animal.

Pathway of Zoonotic Disease 

In direct zoonosis, the disease is directly transmitted from animals to humans through media such as air (influenza) or bites and saliva (rabies). In contrast, transmission can also occur via an intermediate species (referred to as a vector), which carries the disease pathogen without getting sick.

Who is at a higher risk of serious illness from zoonotic diseases?

Anyone can get sick from a zoonotic disease, including healthy people. However, some people are more at risk than others and should take steps to protect themselves or their family members. These people are more likely than others to get sick, and even die, from infection with certain diseases. These groups of people include:

• Adults older than 65
• People with weakened immune systems
• Pregnant women

Impact of Zoonotic Diseases:

“Every year, tens of thousands of Americans get sick from diseases spread between animals and people. 

The impact of zoonotic diseases on human health and the economy is difficult to assess because many of these diseases go undiagnosed, are not nationally reportable, and·can be transmitted from sources other than pets. Considering these limitations, a review of national disease surveillance data and the published literature suggests that over 4 million people in the United States are infected annually with zoonoses transmitted from pets, at a cost of more than $300 million. These costs include those of direct medical care during acute illness (for example, salmonellosis), chronic supportive care (for example, congenital toxoplasmosis), and disease prevention (for example, rabies), but not the loss of life or quality of life resulting from these diseases. Efforts need to be made to prevent the transmission of zoonoses from pets to human beings through appropriate health care of pets to eliminate infectious agents and through educating the public, particularly pet owners, of the zoonotic potential of these diseases, 

so that they may take precautions to minimize the risks leading, to infection.

Impact of zoonoses on human health and economy:

Socioeconomic losses from zoonoses are difficult to quantify completely (as with other human diseases ) because the cost of lives and cannot be measured. Many zoonotic diseases cause serious illness and high mortality in men.

Impact on Health:

The effects of febrile illness include:

• loss of work capacity
• loss of earnings
• clinical complications
• interference with patterns of family life and
• potential malnutrition from increased metabolic demands in people who are already poorly nourished.

Impact on socioeconomic:

• Livestock diseases, especially zoonotic diseases have direct consequences for national economic development.
• They reduce the available supply of needed food, especially high-protein food.
• Feedstocks of grain, grain by-products, and animal by-products are wasted when the animals consuming them die.
• E.g., Foot and mouth disease (FMD) contributes to the problem of human malnutrition in a big way.
• The presence of animal diseases in an area may prevent human habitation. 
• The economic costs incurred in the control of zoonotic diseases in animals are often huge and are additional to medical costs and losses in human work.
• The additional expense arises from surveillance mechanisms for detecting animal reservoirs, diagnosis of animal diseases, quarantine of animals, restriction on animal transport, an inspection of meat and milk, and condemnation of animal products.

How to cope up with Zoonotic Diseases:

PROPER PERSONAL HYGIENE

• Wash hands before and after animal handling.
• Do not eat or drink in the animal housing areas. 
• Wear coveralls, farm-specific clothing, or laboratory coats when handling animals.
• Avoid handling sick animals or animals with lesions unless gloved.
• Wear a mask if you are allergic to animal hair or dander or if feed or bedding dust is present.
• If you are sick, DO NOT enter the agricultural animal facilities.  You are more susceptible to other infective agents and you may transfer pathogens to the animals!
• Routinely wear gloves when cleaning the animal area.
• Note the progression of any illness.  Report illnesses to your supervisor. 
• Inform the physician of your animal-related activities.

ENVIRONMENTAL MAINTENANCE

• Keep animal housing areas well organized and clean.
• Avoid urine and fecal build-up.  Dry feces result in fecal dust which may be inhaled.
• Clean rooms have a lower likelihood of horizontal or zoonotic transfer.
• Proper ventilation protects the animal and workers.
• Clean feed and bedding from floors.  Litter attracts vermin which may introduce a zoonotic disease into the facility.

HERD/FLOCK MAINTENANCE

• Observe animals for health status daily.
• Report sick or dead animals.
• Note health problems such as diarrhea, difficulty breathing, depression, immobile.
• Take extra caution in cleaning the areas around ill animals. Don’t spread possible pathogens.
• Isolate affected animals as appropriate.
• Record history or progression of animal disease.

Sadab Hossain

Faculty of Veterinary Science

Bangladesh Agricultural University