Transmission of Infections from Pets to Man

Transmission of Infections from Pets to Man

Most of the infections humans suffer today are transmitted to them by animals. These infections (systemic and superficial) can lead to death, which in most cases affects the entire population. These animals are kept in homes and individuals relate closely with these animals referred to as pets and in the process transmit microbial infections to man who co-exist with them.

An Overview of Pets

According to the BBC English dictionary, a pet is an animal people keep in their homes to give pleasure and company. According to the Longmans English dictionary pets are animals people keep in their homes and look after them. According to the chambers universal dictionary a pet is a tame animal people keep in their homes.

In most cases pets are wild animals, though, domestic animals can also be used as pets depending on the choice of specie of animal the individual wants to keep as a pet. (BBC English dictionary).

Relationship Between Man and Pets

Los Angeles country has 2.6 million privately owned cats and dogs. There are over 1,000 pet stores in Los-Angles country our population of companion animals (pets) countries to increase with approximately one person in five owing at least one animal. Many of these animals have intimate contact with their owners. This increases the chances of transmission of microbial infection or animal diseases to humans. Individuals relate with their pets in different ways some people eat with their pets. Others sleep with their pets other have their baths with their pets in the bathtub others go everywhere with their pets. This thus creates a chance for the transmission of microbial infections from pets to man. Despite the fact that some people have a very good relationship with their pets, some or a number of individuals who keep these companion animals hardly relate with their pets. (Acha and Szyfres, 1999).

Some Animals Used as Pets         As stated earlier most of the animals used as pets or companion animals have been tamed. These animals are gotten or obtained from different sources in different countries from the zoos or parks. These animals among others include. Snakes bears, crocodiles, turtles, alligators, elephants, monkeys, zebra, dogs. Although, domestic animals could also be used as pets depending on the choice of species the individuals desire to keep as a companion animals.

Exotic Pets

In 1997 (West hills) a woman’s dog was devoured by a twenty-five pound, seven and a half foot Boa. This raised community alarm or concern about exotic pets and the hazards associated with them. In Los Angels over 80% of the exotic pets are reptiles. In 1995, it was estimated that 7.3 million pet reptiles were owned by approximately 3% of households in the United States. Between 1994 and 1995, health departments in 13 states, carlifornia inclusive reported human infections with unusual salmonella serotypes to centers for disease control. Many individuals have contact with reptiles, and salmonella species were isolated from 36% of these reptiles that has contact with humans during surveillance activities. (BBC English).

Usefullness of Pets

Companion animals are kept for different reasons to some pets serve as a source of companionship. Researchers or scientist keep pets as laboratory animals to carryout laboratory examinations. In movie and entertainment industries pets have also been found useful. Pets are also kept in order to get rid of rodents in our homes.

‘Ways Through which pets participate in the Transmission of Pathogens.

Most of the infections that occur in man are as a result of contact with pathogens. These pathogens get to man through different ways. Animals have been implicated as a source of microbial infections which they transmit to humans. (Turk and porter 2003).


A reservoir of infection is sites in which organisms can persist and maintain their daily to infect other host when transmission occurs. Animals, which or those humans keep as companions in most cases are reservoirs of infections. Thus they habour pathogens which they transmit to humans after the pathogen has been amplified in their systems. Thus, as these animals being reservoirs of infections co-exist with man, the pathogens in their system moves into the system of man, replicates and cause microbial infections which might lead  to death (Acha and systems 1998).

 Zoo Noses:

Infections that occur naturally among animal species now occur in humans there infections are known as zoonses. Thus, the animals humans keep as companion can transmit animal infections to human, which could lead to pathological condition. The rabbies virus can thus be transmitted to man by dogs, since humans now suffer most of the infections, which are naturally suffered by animal species.

Pets as a Source Of Pathogens

Except when lowered local or general resistance makes a person susceptible to the attack of his resident microorganism, pathogens are always exogenous i.e. They come from outside except in few cases of fungi and some clostria. Thus pathogens come from other humans or animals, pets inclusive. These animals may themselves be clinically infected or may be carriers transmitting pathogens to other host without showing any evidence of related disease. Thus, it can be said animals are a source of pathogens which they transmit inwardly to a new host. (Hoeprich et al 1994).

Portals of Entry For a disease to successfully infect humans and cause pathogical conditions, the pathogen must enter the human body and find its way to a location that it is capable of adhering to and grow. Alternatively the pathogens produce toxins. (In the case of food poisoning), but the pathogen must first enter the body, pathogens have well defined portals of entry an are not infectious when they inter a wrong portal of entry. These routs via which the pathogens enter a host are called portals of entry. These include; mouth ears, eyes, nose, broken skin, insect bites surgical wounds e.t.c, often but not always the characteristics of the disease gives reasonable clues as to its portal of entry. Thus, for a pathogen to cause infection it must successfully enter these routes of entry. (Turk and porter, 1978).

– Skin              Wounds, abrasions, bites, follicles, injections

– Respiratory tract    Inhalation

– Alimentary tract     Ingestion

Genital tract             Sexual intercourse

Placenta                   mother to foetus.

Portals of Exit

Pathogens typically exit from animals via their body fluids including saliva respiratory fluids, feaces, sputum, semen, vaginal fluids, Urine, blood. As these pathogens exit the animals through these routes they are transmitted to humans or other animals. (Turk and Porter, 1978).


A vehicle is a substance that is normally brought into the body. These include H20, air, and food. Thus vehicles are not formites and formites are not vehicles. Formites are inanimate objects such as clothing and personal possessions. Most especially pathogens with anal portals of exits may contaminate H20, thereby, transmission via H20 occurs, and this kind of transmission is termed as indirect feacal – oral transmission. Air, especially dry air exposed to sunshine is a hostile  environment for many pathogens. Nevertheless, some air borne transmission occurs. Food-borne transmission like water-borne transmission is usually of gastrointestinal pathogens. Thus most pathogens are transmitted from animals to man with the aid of a vehicle. (Turk and porter 1978).

Modes of Transmission

Transmission is the movement of pathogens from one host to another host resulting into clinical or sub-clinical infection. An infection is the entry and replication of a pathogenic microorganism into a host leading to disease conditions. (Word book encyclopedia 1978).

Animals, pets inclusive, may carry pathogens in their systems without showing clinical signs, but ather amplifies the pathogen and transmit the pathogens to humans being an infrequent, thus an incidental host. These infections are transmitted to man by direct or indirect contact transmission (Turk and porter 1978).

Contact Transmission

Transmission by contact can occur directly or indirectly.

Direct Contact Transmission

In the transmission of pathogens via direct contact, the pathogen typically exist from the animals via body fluids; semen, saliva, feaces etc when man comes into direct contact with these portals of exit, transmission via the portals of entry occurs. Indirect contact transmission.

This kind of transmission does not occur directly; instead, contact is made between an or a healthy individual and the disembodied body fluid of a carrier (A diseased animal or man). This occurs via formites which are inanimate objects upon which a pathogen has been deposited. That is, transmission occurs between a healthy individual and a disease carrying formite. (Turk and porter 1978).

 Some Infections Transmited from Pets to Man

Animals, including our pets are reservoirs of infections to humans. These infections can lead to serious pathological damage to the host tissue which might even lead to death.

 Toxoplasma Gondi

T GONDI is one of the infections transmitted from animals to man. The parasite has increasingly become recognized as an important pathogen in wild and domestic animals, the cat family per se. the parasite is an obligate intracellular protozoan. The definitive host being members of the cat family in nature. (Ikeh 1999).

In the cat the parasite possesses both the enteroepithelial and extra intestinal cycle. In the incidental host such as man, all order of mammals, birds and probably reptiles, it exist in the extra intestinal cycle. The parasite has three forms the tachyzoite (previously trophozoite), the tissue cyst and the Oocyst (in which sporozoites are formed bradyzoites (Ikeh 1999).


Oocyst excreted by cats are transmitted to incidental host. The protozoan invades the intestinal epithelium and disseminates widely to all host tissues. This can occur in domestic animals. As high as 25% mutton, 25% of pork samples surveyed have been shown to contain tissue cyst. The Oocyst has rarely been demonstrated in beef (Ikeh 1999).


These are trypanosomatic protozoan parasite with its life cycle involving two host. The parasiste causes leishmaniasis. Reservoirs include; dogs and wild rodents. It is also a zoonotic infection. (Ikeh 1999).

Transmission         Transmission from a reservoir host to an incidental host is via a vector and thus, is initiated by bites of the vector. The female PHLEBOTOMUS sand fly is the vector, and no other vector has been identified. Although infection has implicated causes of blood transfusion, but such cases are very  rare. (Ikeh, 1999).


Animals appeal to be reservoirs for human infections. Human volunteers were infeceted experimentally with girdia cyst from beavers and it caused infection known as girdiansis. The protozoan is flagellated.


Transmission occurs via oral ingestion of the cyst and results in proliferation of tropozoite in the lumen or the upper small intestine. Many infected individuals are asymptomatic, but some experience cramps, malaise and weight loss. (Ikeh 1999).

Concept of Zoonoses

Diseases or infections that occur in animal species and can be transmitted to humans is known as zoonoses. Naturally, zoonosis are disease of animals, but rately these infections are transmissible to man. Thus, zoonoses are infections or diseases which are shared between animals and humans. (Acna and Szyfres 1987).

Most of the human infections emerging today are zoonoses and humans acquired these infections from companion animals directly or by eating products of animal origin. A large number of the animals humans keep in their homes habour zoonotic agents which they transmit to man leading to microbial infections. (Gorback et al 1992).

 Reverse Zoonoses

Human diseases in some cases can also be transmitted animals, such diseases are known as reverse zoonoses. Most recent outbreaks of reverse zoonose started in 1996 with the death of two circus elephant with extensive tuberculosis, involving over 80% of their lungs. In 2004, an elephant with tuberculosis died at the Los angeles zoo. A second one with tuberculosis was transferred to sanfransisco (Lederber and shope 1992). Infected with human salmonella. (Available at htt:// LatesNews and dispay = 2080.

E. coli and listeria are two other common infections  caused by zoonotic agents which can also lead to pathological conditions (Gorback et al 1992). Many other zoonoses apart from salmonella, camphylobacter etc are of medical importance and thus their causes should be  controlled if known. In the case of CJD, Lancet reported in 1997, that CJD was associated with consuming squirrel brains in people in Kentucky, people scrambled squirrel brains with eggs or put them in stew. This observation, thus requires confirmation by studies of larger populations and search for a prion agent in the brain of squirrels. (Berger et al. 1997).

Infectious Agent Disease in Animals Disease in Man
Alpha viruses Noapparent disease

animals die of encephalitis


Flaviviruses No apparent disease Encephalomyelitis and Encephalitis
Yellow fever virus No apparent disease animals die Yellow fever
Rabbies Virus No apparent disease Death with paralysis Excitation paralysis and Death.


There are other infections common to animal and man not stated above, these include, murine tyhus, Dengue fever, rocky mountain spotted fever, etc. (Hubbert et al 1998).

Animals as Sentinels

Over 100 years of experience has shown that animal and human health is closely related. Like people, domestic animals and wildlife are exposed to infectious disease and environmental contaminants in the air, soil, H20 and food and they can suffer from acute and chronic diseases from such exposure. Often animals serve as disease sentinels, or early warning systems, for the community. Using animals are a sentinel offers an advantage; lower cost, shorter latency of disease development and greater ease of obtaining tissue sample and autopsy data. Sentinel animals have shorter life span than people and diseases with long latency periods will manifest themselves in sentinel animals before people. To understand that is happening in animals requires regular and systematic analysis of data to identify health hazards. Sick animals can alert people to environmental dangers just like a barking dog alerts its owner of an intruder. (Acha and Szyfres 1999).

Animals, Public Health and the Future

Today infectious animal diseases are a major cause of morbidity and mortality in los Angeles country. This disease will persist beyond our life –times therefore prudent measures must be taken today to prevent and control disease tomorrow. Controlling disease now, reduces our future health expenditures. Treatment of end stage disease can be very expensive and may not be effective. Close agreement on importance of surveillance and an active, trained work force to control disease exist among public health professionals. Disease surveillance/ prevention/control requires a solid foundation in basic detection and control measures. Control of disease can be accomplished only via concrete specific actions geared toward protecting the community as a whole. (Acha et al i987).

There are more than 200 diseases of animals transmissible to people (zoonoses) currently causing a wide variety of illness, in addition as yet undefined zoonotic disease probably exist that pose infectious risk for people. Thus, the significance of zoonoses in the emergence of human infections cannot be overstated. Effective control of human zoonoses first, or concomitantly, requires control in animals. The world is becoming smaller as we are in the twenty-first century. We increasingly find that our neighbours disease problems become ours. (hoseprich et al. 1994).

 How To Prevent The Transmission Of Pathogens From Pets  To Man.

Reports of various infections transmissible to man by pets increases  daily and thus measures should be carried out to control or  eradicate these infections.


To ensure that infections are not transmitted from companion animals to man, it is expedient that pets are vaccinated before they are kept in homes. In carlifornia per se it is required that all dogs be  vaccinated to protect the community citizens from the fatal disease rabbies. (Sechultz et al 2001).


When there is an outbreak of disease it is expedient that the health workers be notified. These gives a basis for the collection of data on the emergin infections and control measures will thus be embarked upon. The figures obtained from the data’s collected from the reported cases of infection is then carefully interpreted, since it is likely that many human infections go unrecorded because either patients fail to report the illness, or because no laboratory diagnosis is made, or because the diagnosis not reported centrally. In the EU per se there are reports on trends and sources of zoonotic agent in animals, feeding stuff food and man. This aids in the prevention of zoonoses via harmonized surveillance system. (Available at httL//europa.Eu.Int/comm./food/fsp mr/ mr08en.pdf.)

Food Safety

Majority, zoonoses are transmitted to humans by eating products of animals origin or contaminated food. The scientific committee on veterinary measures relating to public health published in April 2000 an opinion on the control of zoonoses along the food  which calls for tigher controls and improved monitoring to reverse the trend towards an increase in    zoonotic disease in the last decades. The committee identified seven food– borne zoonoses as the highest public health priorities in this area in Europe. Thus if the food is checked to ensure its safety before it gets to the consumers zoonoses would be eradicated, and the number of people that suffer from food-borne illness which can sometimes be fatal especially salmonelllosis would be reduced. This would be a major step in the prevention or complete eradication of food-borne illness. Available at (http://www. AREA = Latest News and Display = 2080.)

Routine Check –Ups

Companion animals should be taken to see the veterinarian from time to time. If this is embarked upon whenever these animals habour microbial infections it would be detected and controlled immediately.

Proposals And Research Based Programs

To eradicate zoonoses research proposals and programs should be embarked upon. Proposed directives on monitoring zoonoses will lay down a system for monitoring certain zoonotic agents throughout the human food and animals food chain. Countries in addition will be required to take part in co-ordirated monitoring programmes in order to establish baseline values on the level of most important zoonotic infections in each country. Available at ( News and display = 2080.

Chemotheraphy of Some Infections Transmitted from Pets To Man.

Microbial infections transmitted from pets to man can be arrested with the use of drugs for theraphy. In cases of zoonoses antiamoebic drugs can be used to inhibit the microbial activity of the pathogen. These drugs among others include. Tetracycline, fumgillin, diodoquin, vioform, carbarsone. Bismuth, mepacrine, metronidazole, imidazole and furazoli (Ikeh 1999). Antiprotozoan drugs includes among others pentamidine pyrimethamine, paronomycin sulfate, emetine, dioxamide furvate and dehydroemetin.


        This study gives us reasonable dues of the possible source of infections which in this case involves our pets. Pets are extremely useful to the individuals who keep them. Although, if they are not given proper medical attention, keeping them around humans would not be  completely  safe. Thus, pets should be properly cared for especially in developing countries including Nigeria.



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