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Human Lifestyle in Contact With Dogs and Risk of Infection With Protozoan Parasites


1 Department of Parasitology, Faculty of Medical Sciences, Arak University of Medical Sciences, Arak, IR Iran
*Corresponding author: Mahdi Mosayebi, Department of Parasitology, Faculty of Medical Sciences, Arak University of Medical Sciences, Arak, IR Iran. Tel: +98-8633664070, Fax: +98-8634173521, E-mail: mahdi_mosayebi@yahoo.com.
Islamic Lifestyle Centered on Health. 2013 December; 1(4): e12461 , DOI: 10.5812/ilch.12461
Article Type: Review Article; Received: May 25, 2013; Revised: Feb 22, 2013; Accepted: Mar 15, 2013; epub: Dec 20, 2013; ppub: Dec 2013

Abstract


Context: Dogs, as reservoirs, safe carriers and vectors, play an important role in the lifecycle of more than 60 zoonotic diseases. Some of these infections are distributed worldwide and cause serious health care problems and huge economic loss. The agents of some of these diseases are protozoan parasites. Changes in the lifestyle may result in suffering from new infections, or preventing them.

Evidence Acquisition: In the current study, positive and negative angles of contact with dogs were evaluated, and available data and statistics regarding zoonotic parasites, parasitology references, articles, narrations and traditions from Holy Prophet (PBUH) and infallible Imams (AS) in Persian books and websites were also studied.

Results: The current study evaluated the zoonotic parasites, and their similarities and differences; it also expressed probable risk of transmission of some zoonotic parasites from dogs to man and vice versa, how to interact with dogs, the important role of this animal in the infection and prevention of zoonotic diseases, and how to cope with dogs in Islam considering Islamic narratives and traditions.

Conclusion: Many of the books and papers have indicated the role of dogs, as an animal reservoir in transmission, storage and survival of protozoan parasites in the nature. The narratives of infallible Imams (AS), along with emphasis on Islamic lifestyle have considered this animal specifically , and with emphasis on the animal`s rights have considered dogs as unclean animals and have warned people not to contact with dogs and the necessity of practicing hygiene in the case of keeping this animal. Islamic lifestyle may play an important role in decreasing zoonotic diseases.

Keywords: Dog; Protozoan; Lifestyle; Traditions; Human

1. Context


Domestic animals have many advantages for the people and human societies, but on the other hand, their potential to transmit the pathogens to man should be considered (1). One of the most popular pets is dog (Canisfamiliaris). Dogs are domesticated wolves, and probably belong to the one of the following subspecies: Canis lupus pallipes, or C. lupus variabilis (2) which around 12 to 15 thousand years ago were domesticated by man, and closely participated in human activities such as hunting, guarding, sheepherding, and finding food. This participation is still continued after many years in different cultures, and by entering dogs to human residential places as pets, has turned into a new form. Today, dogs play different roles such as sport, working, hunting, play and fun, and rescue dogs in finding food, sheepherding, law enforcement, guarding, finding drug, fighting with terrorism, helping blind and deaf people, and also in medical laboratories and vaccine production.


Some people believe that dogs are faithful and useful animals for better and happier life, especially for the isolated people. In some countries, even dog meat is consumed as food. Trained dogs are also employed in the rescue of people with cardiovascular and mental diseases. Despite all these benefits, dogs are isolated animals in some societies because of hygienic and religious reasons. Dogs are the reservoirs, safe carries, and vectors of some viral, bacterial and parasitic (protozoan or nematode), and zoonosis infections which are occasionally transmitted to man, directly or indirectly, through close contact, or environmental pollutions, and vector insects. Some of these infections are spread worldwide and cause serious issues for the general health, and economic losses. Biting, disease transmission, harassment and noises, killing hens, polluting the environmental with stool, tearing garbage bags, and over reproduction are among hygienic problems caused by dogs (3). People treat dogs differently based on their cultural, social and religious background. Muslims, considering religious teachings, do not have much contact with dogs, except for some necessary and useful cases. In the Islamic societies, there is no limitation in using dogs in hunting, guarding, security, sheepherding and some other cases. Useful and harmful angles of contacting with dogs, considering available statistical data regarding diseases, and also evaluating Islamic viewpoints about the way to contact dogs play an important role in prevention and control programs of zoonosis diseases in the Islamic countries.

2. Evidence Acquisition


The current study investigated the useful and harmful angles of contacting with dogs, available statistical data regarding diseases, articles, narratives cited in Persian books and websites, zoonosis protozoan parasitic diseases, and the way to treat dogs.

3. Results


Dogs are hosting various parasites, microorganisms, and viruses, and play an important role in the lifecycle of 60 zoonosis diseases that rabies, echinococcosis, and toxocariasis are among the most important ones (4). More than 90% of patients infected with rabies die annually (5). Dogs cause hygienic problems directly and indirectly. Public environments such as beaches, parks, and playing fields are full of dogs and cats stool, which is the main source of the infections (6). Only in USA, some thousand tons of dog stool, and some million liters of dog urine enter the environment everyday (7). According to a study, 60% of children playgrounds are contaminated with different parasites ova, especially toxocara (8). Different microorganisms have been isolated from dogs which may have considerable health risks for their owners (9). Owners of the dogs are considered as high risk groups, and contact or keeping some dogs increases the risk of infection. People such as sheepherders, ranchers, nomads and veterinarians, who have more contacts with the dogs because of their occupation, are at higher risk. In the study conducted on zoonotic parasites transmitted by dogs, it was found that physical contact between dogs and their owners is normal. Therefore, the risk of zoonotic pathogens transmission among them is high (10).


3.1. Role of Dogs in Protozoan Zoonosis Diseases

Studying zoonosis diseases based on accurate taxonomic information is about their agents. If zoonotic parasites have genetic affinities, there is the probability of their transmission between the hosts, one-way or two-ways, with the same prevalence; but if their genome is different, transmission will rarely happen. Isolation of the same parasites in the dog and man as hosts does not show the way of transmission and more ecologic studies should be conducted to diagnose the source host and the reservoir. In another study, the prevalence of isospora, sarcocystis, giardia doudenalis, and cryptosporidium in the dogs understudy were 12%, 10%, 9%, and 5%, respectively (11); however, the exact role of dogs in transmission of these parasites needs more researches.


3.1.1. Intestinal Flagellates of Dogs

Trichomonashominis: Pentatrichomonashominis is a microorganism isolated from human and dog (12). Since trichomonads have no resistance cystic form, they can be transmitted from dogs to man in close contacts.


Giardia lamblia: The prevalence of this parasite, based on different sampling methods, in the different regions of the world is ranging from 1 to68% in South America, West Europe, and Australia (13). Results of some studies indicated the prevalence of this parasite in the USA between 5.2% and 7.4%, and have emphasized on the transmission of this parasite from dog to dog, in the areas contaminated by the stool of reservoir dogs (14). Results of these studies indicated the low possibility of zoonotic transmission of giardia. Giardia lamblia is the human form of this parasite, and its zoonotic form is called Giardia deoudenalis with similar morphology; dogs are mostly infected by this specious, but G. intestinalis genotyping showed that there are some differences in the small rRNA subunits of human and dog isolations (15). In molecular studies, some differences were observed among parasites isolated from human and animal hosts, and also parasites isolated from human and dog (16). In some other studies, human and animal isolates have been categorized in three molicular types. Dogs are the host for G. doudenalis (genotype A and B). Sometimes dogs are contaminated by A1 subcategory, which is also isolated from human, but dogs are usually contaminated by A2, which in this case giardia is potentially zoonosis (17). In the study conducted in this regard, only 0.6% of the stool of dogs of urban areas transmitted the most potential zoonotic parasite, subgenotype A1 (18). To evaluate the level of sensitivity and contamination of dogs, human isolates, G. doudenalis in two groups as cystic, trophozoite, and a control group were inoculated to dogs. Results showed that human G. doudenaliscan isolations could infect dogs without clinical symptoms (19). In the societies where the stool is not excreted safely, dogs are at risk for contamination with the parasites transmitting through the stool. In another research, Giardia spp. is reported as the most prevalent parasite among dogs (20). To prevent and reduce the contamination symptoms in dogs, giardia vaccine has been designed which reduces fecal cysts in dogs and cats, and prevents infection symptoms (21).


3.1.2. Entamoebahistolotica

Amebiasis is the second protozoan disease, after malaria, and the third deadly parasitic agent, after malaria and shistosomiasis, in the world (22). Beaver believes that normal contamination of dogs to E. histolitica, probably results from eating human stool containing cysts, considering the fact that this parasite does not produce cyst in dogs (23).


Entamoebacoli: it is the most common human ameba in the world. The cysts of this parasite can almost be found in all societies. Few reports on the contamination of dogs to this parasite is available which has been probably caused by eating human stool.


Acanthamoeba spp.: Acanthamoeba is a free-living ameba which causes keratitis in people who use contact lenses, and causes skin irritations in the people who suffer from immunodeficiency. Granulomatous encephalitis in human usually causes death. Soil and water strains of amphizoic amoeba have worldwide distribution (24). Human infecting specious have been also isolated from dogs (25), but the probability of parasite transmission from one host to another is weak. It seems that all parasites have been transmitted from the environment, independently.


Entamoebagin givalis: This ameba lives in human mouth, and is transmitted from one person to another directly through oral contact, or probably by contaminated dining facilities. According to the conducted studies, E. gingivalis can be transmitted to the dogs suffering from gingivitis, but cannot be transmitted to dogs with healthy gums (26). Normal infection is sometimes observed in the dogs; therefore, normal transmission of the parasite between human and dogs, through direct or indirect oral contact, is theoretically possible.


Entamoebahartmani: This avirulent ameba is harmless and lives in human and primates gastrointestinal tract. This parasite causes colitis in dogs and cats (22).


3.1.3. Intestinal Sporozoans

Cryptosporidium parvum: A zoonotic parasite which causes diarrhea in the newborn beefs. Until 2007, 16 different specious of Cryptosporidium spp. were found, and more than 33 genotypes were described (27). Cryptosporidium parvum cause short-term diarrhea in human in the normal conditions. This parasite causes acute untreatable diarrhea which is usually killing, in people suffering from immunodeficiency, especially AIDS patients (28). One of the ways of contamination is transmission from animal to human (29). Hence, contact between AIDS patients and dogs is concerning. Cryptosporidium spp. preserve themselves among dog population, and some references believe that dogs are the main reservoirs of this parasite for humans. Close relationship increases the possibility of parasite transmission from dogs to humans. Unfortunately, people suffering from acute immunodeficiency and children with malnutrition are infected with the dog and cat cryprosporidiosis (30).


Cyclospora cayetanesis: This parasite is mostly known as the cause of sporadic and sometimes epidemic diarrheas. Contamination to Cyclospora spp. has been also reported in primates, baboons, and probably chimpanzees. A study reported that this parasite was isolated from two dogs and accordingly, it is thought that the dog is the host for this parasite (31).


3.1.4. Other intestinal Protozoans

Blastocys tishominis: This is one of the most common human parasites. This avirulent protozoon may cause chronic and uncontrollable traveler’s diarrhea in tourists and travelers (32). This parasite is deployed in the gastrointestinal tract of humans and a wide range of animals (22). It has been reported that this parasite has been also isolated from dogs. In a study, the test result of 43 dogs out of 60 was positive; and in another research, 70.8% of the tested dogs were contaminated to this parasite. Transmission ways for this parasite are fecal-oral, taking contaminated food and water, and close contact with the contaminated animal (22).


Balantidium coli: this parasite normally lives in the large intestine of pigs, dogs, primates and sometimes humans, and other mammalian hosts. This harmless organism, sometimes becomes aggressive, attacks intestinal mucosa of its host and causes intestinal disease. This organism has been isolated from human and dogs (23).


3.1.5. Parasites of Blood and Other Tissues

Leishmania infantum: This parasite causes Mediterranean-visceral leishmaniasis in human, which its development causes death if untreated. This parasite is one of the most important zoonotic protozoans which dogs are their reservoirs. Dogs play an important role in the transmission of this specious to human, from Africa to Europa and Asia, especially from Europa to South America. Canine-visceral leishmaniasis is widely common in South and Central America (33). The largest population of this parasite in nature is in dogs. The main reservoir of this parasite is the domestic dog and they are mostly transmitted through dogs (34). Contamination of foxes is through shepherd dogs, and farm watchdogs. Evidences have been also provided regarding another animal reservoir for this parasite, but in South America only wild canine is the reservoir. Results of the conducted studies indicate the role of dog flea in the lifecycle of Leishmania spp. (35).


Leishmania tropica: this parasite causes cutaneous urban or dry leishmaniasis which has been mostly distributed in the urban areas of west and Central Asia from north of India to Syria. Contaminated dogs are the main host or reservoir of this parasite in India, Afghanistan, and Iran.


Leishmania major: usually contaminates desert rodents, dogs are not important hosts. This parasite has been rarely isolated from the dogs in Saudi Arabia.


Leishmania braziliensis and Leishmania peruviana: Leishmania braziliensis: This parasite causes cutaneous-mucosal leishmaniasis and destruction of large areas of patient’s face, and widely lives in the forested areas of Brazil and neighboring countries such as Bolivia, Ecuador, and Colombia; but Leishmania peruviana rarely cause these problems, and mostly cause diseases limited to the initial wounds. This disease is observed in the alpine valleys of western foothills of Peruvian Andalusian, and probably Ecuador. Both specious mostly exist in animals, and they have been also isolated from wild animals as much as domesticated dogs. In the study conducted on the role of dogs as a reservoir for cutaneous-mucosal leishmaniasis, it was shown that the contamination of dogs to these two specious can be found in all human contaminated areas (36).


Trypanosoma brucei: Sleeping sickness or African trypanosomiasis is one of the tropical diseases which tsetse fly is its carrier. This parasite can be found in three subspecies:


T. b. brucei: it is not harmful for human, but kills the dogs.


T.b.rhodesiense: it is a zoonotic parasite and can be found in wild life, and causes acute sporadic and endemic diseases in human.


T. b. gambiense: usually likes human and causes short-term disease in human. This parasite has been isolated from wild animals, pigs, and dogs, and its main reservoirs cannot be detected.


Trypanosoma cruzi: infection with this parasite is widely distributed from South to North of America, in the areas which contaminated dogs are living. This parasite is transmitted between its mammalian hosts through triatomine bugs. Contamination of human to this parasite is asymptomatic, or causes lifelong illness with the chronic changes in heart which causes heart failure, or leads to acute disorder in the performance of intestines. In human residential areas across Latin America, dogs are contaminated to this parasite and can be the important reservoir for human infections. In the northern area of Argentina, abundance of Triatomainfestans bugs has direct relation with the level of contamination in dogs, but has no relation with the level of human contamination (37). The probability of contamination of each bug to this parasite, if bites dog, is 500 times more than when it bites human, and considering the interest of T. infestans bugs in biting dogs, there is no doubt that dog is the main and most important reservoir for this parasite in these areas. Dogs are the main reservoir for this parasite, because of close contact with human and their own high contamination. Contamination of dogs usually happens in the human residential areas; in a way that decreasing the level of transmission may simultaneously affects contamination of two hosts as human and dog (38).


Toxoplasma gondii: dogs, like human and other mammalians, are intermediate hosts. Dogs may be infected with the excreted oocytes of parasite through touching the stool of cat, and can transmit the infection to their owners mechanically (39).


Babesiagibsoni: this is one of the dog’s parasites, and a parasite similar to Babesiagibsoni (WA1) contaminates man in America. According to the conducted studies, parasites isolated from human cannot contaminate dogs, but they can contaminate some species of rodents (40).


Microsporidia: the specious as Encephalitozoon cuniculi is probably zoonotic. This genus and specious has many hosts among rodents, rabbits, and sometimes dogs, foxes, wild carnivores, and primates such as human. Prevalence of infection among canine, based on research methods and populations understudy is different. Studies revealed that the dogs are the reservoirs for the transmission of E. cuniculi to human (41).


3.2. Islamic Lifestyle and Relation With Dogs

Different narratives and traditions have been cited from Holy Prophet (PBUH), and infallible imams (AS) that contain important notes regarding how to keep or cope with dogs if necessary; considering all these factors, the viewpoint of Islamic lifestyle regarding the dogs can be perceived. In some narratives, drinking and ablution with the leftover water of some animals is permissible, but drinking and performing ablution with the leftover water of dog is forbidden. Drinking the leftover water of dog is not permitted, unless it was drunk from a big pond. Also, eating the leftover food of dogs, or contact with its stool is not permitted, and it was emphasized on washing the bowl which dog drinks from it with water and soil. Accordingly, eating or touching dog meat is forbidden.


Drinking and performing ablution with the leftover water of the dog has been avoided in some narratives cited from Imam Sadigh (AS), unless the dog was drunk from a big pond (42).


Ibn Muslim said: I asked Imam Sadigh (AS) that: “what should we do if a dog drinks water from a bowl? He answered: “you have to wash the container. Or in another narrative he added: “throw-out the water which the dog has drunk of it (43, 44). Also, washing clothes, body, or hands which touched or damped by dogs have been emphasized.


Imam Sadigh (AS): “if you contacted the humidity of dog, then wash your clothes” (43).


Muhammad Bin Muslim asked the Holy Prophet (PBUH) about the kind of hunting dogs; He answered: “if you touched it, wash your hands” (45).


Imam Ali (AS): “avoid getting close to dogs, and if you touched a wet dog, wash your clothes, and if it was dry, splash water on your clothes” (46).


In some narratives, praying in the house which dog lives in it, without separating door or wall, is wrong; and keeping dogs in Muslims’ house is unacceptable. According to the Islamic narratives, keeping dogs decreases religious obligations.


Muhammad, the holy Prophet (PBUH): “Gabriel came to me and said: “we angels do not enter the home in which there is dog, its statue, and its urine container” (47).


Imam Sadigh (AS): “do not pray in the house that there is a dog in it, unless it was a hunting dog and a door separates it, so it is ok” (48).


Imam Sadigh (AS): “it is unacceptable if a Muslim keeps dog in his house” (47).


Imam Sadigh (AS): “no one keeps a dog, unless his religious obligations decrease everyday (49).


Some narratives have noted the conditions for keeping dogs, such as hunting dogs and shepherd dogs, there should be a separate place for the dog, and a door to separate it.


Amir al-mumenin, Imam Ali (AS) said: “it is no good to keep dogs, unless hunting dogs and shepherd dogs” (49).


Imam Sadigh (AS) said: “do not keep the hunting dog in your home, unless there is a separating door between you and it, and it lives in a separated place” (49).


According to some narratives, keeping dogs is considered as ethical vices such as drinking wine, and debauchery, and etc., and noted it as a reason for punishment or prevent allegiance; playing with dogs has also been avoided in Islamic narratives.


Imam Hussain (AS) said: “I will never swear allegiance to Yazid, since he is a lecher man who has uncovered his debauchery, drinks wine, plays with dogs and etc. (42).


Imam Hussain (AS) blamed Muawiyah by a letter and wrote him that: “aren’t you the person who appoints a boy who drinks wine, and plays with dogs?” (42).


Imam Ali (AS) blames Manzar bin Jarood who was appointed by him as the governor of some part of the Islamic lands, through a reprimand, after receiving reports on his violations and betrayals: “it has been reported that you are always engaged in traveling, hunting and playing with dogs (49).

4. Conclusions


Indicating the diseases transmitted by dogs, or through relation with dogs, may affect the promotion of Islamic lifestyle to avoid contact with the dogs, prevent keeping dogs and transmission of zoonotic diseases. Anyhow, in the case of absence of these diseases, no change will be made to the fact that dogs are unclean. Evaluating advantageous and disadvantageous aspects of relation with dogs, and considering the available statistical data regarding zoonotic diseases, are very important to plan the controlling and preventing programs on zoonosis diseases.


Studying Islamic references indicates that the Islamic lifestyle has paid particular attention to dogs, and along with emphasizes on the rights of this animal, believes that it is unclear, and has recommended avoiding contact with it and observing hygienic issues, in the case of the necessity to keep it.


Domesticated dogs are the reservoir for many human pathogen agents, such as protozoan’s parasite. Dog is an occasional host for some protozoans, and the reservoir for some others, especially for Trypanosoma brucei and Leishmania infantum; dogs are the main reservoirs of human pathogens and these two parasites are from the most important and dangerous human protozoan pathogens. Changing lifestyle may result in the new infections or may prevent these diseases; here veterinarians, physicians, and religious scholars play an important role in warning risks and promoting safe lifestyle.

Footnotes

Author’s Contributions: All searching, translating, taking notes, summarizing, and setting the article have been performed by Mosayebi M., PhD.
Financial Disclosure: This research has received no financial helps, and was merely conducted by the author.
Funding/Support: To conduct the current study, library and IT references, and administrative facilities of University of Medical Sciences of Arak, Iran were used.

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