Benefits and Risks of Domestic Cats

Pet animals, particularly cats and dogs, play an important role in societies worldwide. They are important companions in many households, contributing to children's physical, social and emotional development and their owners ' well-being, especially in the elderly.

The domestic cat (Felis silvestris catus) is one of the most popular pets all over the globe. According to IFAH Europe (The International Federation for Animal Health Europe), apart from stray cats, there are about 220 million cats throughout the world. Since ancient times, cats have been companions to humans. Egyptians are often credited for the first domesticating African wild cats around 4,000 years ago. Ancient Egyptians considered cats as sacred animals, and mummified cats were found from their tombs. Recent findings suggest that cats may have been closely associated with humans as long as 9,500 years ago. The oldest archaeological evidence of cat taming was found in Crete dating back to approximately 9,500 B.P. and remains of cats have also been found from Jericho near the Jordan River dated to 8,700 B.P.

The most widely accepted theory of cat domestication states that cats essentially domesticated themselves. Cats usually live a solitary existence and maintain their own territories, which makes them more attached to places than to people. Moreover, even their role as mousers is debatable as cats are known to not perform directed tasks. Terrier dogs and the ferret are more suitable in this latter role. For the same reasons, there is little reason to believe the wildcats have been actively sought out and selected as utilitarian companions by an early agricultural community. Rather, the best inference is that people simply tolerated wildcats utilizing human environments and, over time and space, pet cats gradually diverged from their wild relatives.

The evolution and elaboration of agriculture in the Middle East around 11,000 years ago, and the associated expansion in cultivation and storage of grains, such as barley and wheat, attracted the unwanted attention of small rodents, the natural prey of wildcats. Attracted by this increase in the local small rodent population, Neolithic towns and villages were invaded by wildcats who gradually settled there. The human inhabitants there allowed these wildcats to live around their rodent infested homes and granaries seeing the benefits. This process, in turn, gave rise to urban domestic cat populations that became more relied on humans for shelter and food. Thus, the original domestic cat was a product of natural selection whereas adaptation in other barnyard animals and dogs to human dominion was largely driven by artificial selection.

At some point, animals went from being utilitarian companions to “pets”, although it is not clear what the crossover involves. Studies have suggested that both human and animal companions are benefited in many ways by the relationship between them. The relationship between human health and pet ownership has been studied from various perspectives, and there is evidence suggests that pets provide companionship and also probably provide psychological and physiological health benefits.

Research shows that companion animals can physically and psychologically benefit their owners in many ways such as: they have been shown to lower blood pressure, decrease heart rate, helps overcome stressful situations, reduce depression and feelings of loneliness and improve self-esteem, and seemingly do so in diverse contexts. The risk rates for cardiovascular disease are significantly lower for both current and past cat owners than for non-cat owners. Pet owners are reported to use fewer medications, visit their doctor less often, and have lower blood pressure and cholesterol levels than non-pet owners. It is generally believed that pets provide mental and physical health benefits to their human companions.

Several studies have found that owning and/or interacting with a pet has benefits for the individual, including mental health outcomes such as reduced anxiety and physical health outcomes such as improved physical activity and immune response. Older pet owners undertake fewer annual health care visits and spend fewer days in an acute care setting if hospitalized compared to none of the pet owners. In older adults, animals also provide a sense of comfort and social support. Research also shows that pets have an important role in enhancing children's development and in the well-being of the elderly. In a therapeutic setting, pets can also be used.

While animals offer significant benefits to our society, there are well-documented health risks associated with owning a pet. Household pets were found to play a direct role in the transmission of zoonosis. Many helminths infecting humans also occur in other mammals, including domestic cats, who live near humans and eat similar foods.

The human animal bond has become stronger in modern society with pets playing a major role as a source of companionship, entertainment, and emotional support for their owners. This close contact, however, can also increase the risk of exposure to infectious diseases, as pets have been involved in the transmission of more than 60 zoonotic agents. Some of these parasites cause diseases which can be serious under specific circumstances. The increasing number of companion animals, including cats, poses serious problems for public health, veterinary and socioeconomic problems throughout the world.

There are a diverse range of infections that can be transmitted to humans from domestic cats, including parasitic, bacterial, fungal, and viral diseases. Without veterinary care, domesticated free roaming cats in many countries can cause problems of public health and animal welfare concerns. Indeed, the majority of diseases can be controlled or prevented by the cat owners if they are sufficiently knowledgeable and have the resources to do so. Concerns about the public health hazards of pet ownership have recently increased significantly, and while many potentially zoonotic organisms are associated with cats, enteric pathogens are of particular concern.

The occurrence of feline gastrointestinal parasitism throughout Europe has been investigated by many studies. These pathogens affect from 30.8% to 35.1% of owned cats, as reported in two recent multicenter surveys in Europe. The prevalence estimates vary widely among different countries depending on the parasite species, the study population and the diagnostic procedure used. It should be emphasized that, according to Millan and Casanova, the infection rate reaches up to 100% for stray cat populations due to inadequate control of parasites and access to intermediate hosts. There is rather limited data on the occurrence of helminth parasites in Southeast Asia, which is also true for other endoparasites of cats as well.

Variety of factors affect the epidemiology of cat parasites, including geographical location, presence of veterinary care, habits of the local animal populations, and the season of the year (Yang and Liang 2015). Epidemiological surveillance studies reported in different countries show that owned cats permitted to roam outside have high parasite frequencies. Specific hazard factors for endoparasite contamination featured in the ESCCAP guide includes opportunity to wander, contact with canines/felines outside the occupant family, eating flesh or excrement of conspecifics or eating prey. Additional considerations include animal age (e.g., more frequent deworming of puppies), pregnancy/ lactation status, eating slugs/snails, contact with children or immunocompromised persons (increased zoonotic risk) and travel to certain areas (e.g. endemic Echinococcus spp.).

Cats may harbor a large number of endoparasites, including protozoa, cestodes, trematodes and nematodes (Dantas-Torres and Otranto 2014). Gastrointestinal species are considered to be the most important of all the parasites of cats from an epidemiological point of view. Beugnet et al. (2014) found a higher prevalence of gastrointestinal helminths (25.7 %) among domesticated cats than protozoans (13.5 %). Cats have a wide range of helminth parasites, several of which are of zoonotic importance (Laberthe et al. 2004). The intestinal protozoa and helminth parasites of cats that have been identified by studies in different countries include Giardia lamblia, Isospora spp., Cryptosporidium spp., hook worms, acanthocephalans, Toxocara spp., Physaloptera spp., Taenia spp., Joyexiella spp., Dipylidium spp., Dicrocoelium dendriticum spp., Sarcocystis spp., Entamoeba spp., and Blastocystis spp.. In addition to causing disease in cats, the parasites are of zoonotic importance. Cat-to-cat roundworm transmission usually occurs by oral or transmammary route, whereas hookworm transmission occurs by oral or cutaneous route and whipworm transmission by oral route.

Cat endoparasitic infections are relevant causes of respiratory and gastrointestinal diseases in cats. In cats, infections with nematode parasites, including roundworms (Toxocara cati and Toxocara leonina), hookworms (Ancylostoma tubaeforme and Ancylostoma braziliense), and whipworms (Trichuris spp.), are typically subclinical. However, depending on the parasite species and its abundance, infestations can also cause varying clinical signs in cats, such as lethargy, dull haircoat, vomiting, diarrhoea, poor growth rate, anaemia and sometimes even death, particularly in kittens. Parasitized cats tend to be more susceptible to viral and bacterial infections, as well as to other diseases, thus their health and welfare status are impaired. The manifestation of clinical signs may depend on the particular parasite species, their abundance, the presence of multiple concurrent infections, and the animals ' age and individual immunological status. Kittens and young animals typically have a higher prevalence of infections and associated clinical diseases. However, adult and wild felids also contribute to pollution of the environment and hence to the maintenance of life cycles.

Cats and other felines, can act as reservoirs, carriers, transmitters and definitive hosts for many intestinal parasites. These animals play an important role in parasite transmission to human and other animals by shedding parasitic eggs, larvae, cyst or oocyst in their feces. Cats can therefore serve as a source of infection for certain human parasites and indicate their occurrence in a specific locality. Furthermore, these zoonotic parasites can transmit either by close contact with parasitized animals or by exposure to a contaminated environment.

Cats can be a significant potential source of transmission of zoonotic parasites such as Toxoplama and Toxocara. Toxocara cati is a common gastrointestinal nematode in cats around the world that not only infects young kittens but can also cause toxocariasis in humans. Toxocara cati infections in free-roaming cat populations are of particular concern due to the public health risk and its Neglected Parasite Infection status. This worm is mostly prevalent throughout tropical, subtropical and temperate regions. The infective stage larvated egg of the feline roundworm, T. cati, persists for years in the environment and remains transmissible by accidental ingestion to humans. Nematodes such as T. cati, T. leonina can cause visceral or ocular larva migrans in children, whereas A braziliense and, less often, A. tubaeforme can produce creeping eruptions in the skin of exposed individuals. This debilitating disease is most commonly associated with children playing in uncovered sandboxes or on beaches that free-roaming cats can use for a litter box.