Dogs: Companion or Carrier of Diseases for Human?
BHOOMIKA1*, SONAM BHATT2, VIVEK KUMAR SINGH3, ANJAY1, P. KAUSHIK1
1 Assistant Professor, Department of Veterinary Public Health & Epidemiology, BVC, BASU, Patna-14
2 Assistant Professor, Department of Veterinary Medicine, BVC, BASU, Patna-14
3 Assistant Professor, Department of Veterinary Clinical Complex, BVC, BASU, Patna-14
* Corresponding author- e.mail: sirsant.mannat.09@gmail.com
Abstract:
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Among the pet animals, dog play an important role in humans’ life. Dog provide companion and positive effect on psychological and psychical health of their owners. In addition, dog also act as a source of various zoonotic disease. A zoonotic disease is the disease that are transmitted from animals to humans. The zoonotic diseases are caused by number of causative agents such as bacteria, viruses, parasites and fungi. The disease can be pass to human through the direct contact with infected animals/bite/scratch or indirectly through infected water and food. The important and common diseases of dog is discussed here.
Introduction:
Dog has been kept as a pet animal for more than 14 centuries. Many studies have confirmed the valuable role of pets in life of human being. Many reports have been confirmed that the owing a pet increases the activity of the owners and subsequently helps in reduction of serum cholesterol, triglyceride level, fewer cardiovascular abnormalities. Although dogs have significant positive effects on the psychosocial and psychical health of their owners, many diseases among humans are attributed to them such disease are called zoonotic diseases. Dog act as a reservoir for the many zoonotic pathogens includes; viral, bacterial, fungal and parasitic agents. Zoonotic disease can be transmitted to human through various approaches i.e., saliva, feces contaminated aerosol and direct contact with infected dogs.
The major viral infections such as rabies, bacterial diseases include Pasteurellosis, salmonellosis Yersiniosis, campylobacteriosis, Leptospirosis; parasitic infestations like echinococcosis, Visceral Larva Migrans (VLM), Cutaneous Larva Migrans (CLM) and fungal infections such as ring worm & scabies transmitted to humans from dogs. The causative agent, mode of transmission, treatment, prevention and control are discussed below:
- Rabies:
Rabies is one of the old & deadly disease. According to World Health Organization report it causes 30,000 to 70,000 deaths annually at a global level (WHO, 2020). In Asian countries including India, dogs are the major reservoir for the disease in domestic animals. The majority of the patients in developing countries acquired infection by dog bites while, in developed countries, wild animals including raccoons, bats and foxes are the main cause for rabies transmission.
Etiology: Caused by rabies virus (lyssa virus, ss RNA, enveloped, bullet shaped)
Mode of transmission: In India 99% of cases of rabies in India spread by bite of rabid dog. However, the jackal plays an important role in the transmission of wild life rabies.
Symptoms in human: After bite, the first symptoms will appear in few days to years. Patients may present agitation, anxiety, confusion, hallucination, and hydrophobia and death due to respiratory failure.
Treatment: Washing the wound with water and liquid soap can dramatically reduce the viral load and consequently the probability of rabies infection. The post exposure treatment extensively depends upon the category of bite. The first category comprises the mild scratches without oozing of blood while the category two and three bite consist of multiple bite with laceration. The category one bite can be treated by post exposure prophylaxis (at 0, 3, 7, 14, 21 day) and category two and three can be treated effectively by post exposure prophylaxis along with frequent doses of human rabies immunoglobulin (HRIG) or equine rabies immunoglobulin (ERIG) within 14 days after the suspected dog bite can prevent the disease.
Prevention and Control:
Control the infection in domestic animals especially in dogs. Proper immunization of domestic dogs: vaccination of dogs between 3 months to one year of age. Control the stray dog population. Immunization of risk groups such as veterinarians, dog handlers and laboratory workers.
- Leptospirosis:
Leptospirosis is worldwide zoonoses that are mostly transmitted to human by environmental sources including contaminated soil, water, urine, or tissue of the infected animals. Rodents are the major reservoirs for Leptospirosis; however, domestic animals including dogs can play an important role in leptospirosis transmission in endemic regions.
Etiology: It is caused by the species of genus Leptospira, among this L. interrogans is the major cause of Leptospirosis in human.
Mode of transmission: Direct contact with infected material, through skin abrasion’s and the oral, nasal and conjunctival mucosa. Indirect exposure through water, soil, or foods contaminated by urine from infected animals is the most common route.
Symptoms in human: Fever, non-productive cough, headache, musculoskeletal pain, diarrhoea, nausea, vomiting, alveolar haemorrhage, and even meningitis.
Treatment: Several antibiotics such as doxycycline, ceftriaxone, cefotaxime, penicillin, amoxicillin, and ampicillin have been successfully employed for the treatment of Leptospirosis.
Prevention and Control:
Personal hygiene. Use of protective clothes during farm work. Drainage of lowlands whenever possible. Food protection and correct garbage disposal. Control of infection in domestic animals. Avoidance of swimming in streams and other fresh watercourses that may be contaminated. Chemoprophylaxis of high-risk groups (sugarcane harvesters, rice paddy workers, or soldiers).
- Echinococcosis:
The genus Echinococcus includes several species and genotypes of zoonotic cestodes (tapeworms). The adult stages occur in the intestines of canids and felids without clinical relevance.
Etiology: caused by the species of genus Echinococcus
Mode of transmission: The dog carries parasitic eggs on its tongue and snout to different parts of its body, and a person’s hand can become contaminated by close contact with dogs and deficient personal hygiene practices, such as failure to wash hands before eating are important factors in the transmission of the infection from dogs to human.
Symptoms in humans: Clinical symptoms depends upon the organ effected by the cysts. Majority of cysts in humans are found in liver followed by lung and other organs. Large amount of hydatid fluid absorbed through peritoneal fluid and leads to allergic and anaphylactic reaction. Sometimes the ruptured cyst wall pieces may cause serious complications like bronchial and biliary abscess. Apart from anaphylaxis, when cysts ruptures in the thoracic and abdominal cavity leads to secondary/ disseminated hydatidosis.
Treatment: Drugs such as albendazole and praziquantel in high doses rates have been tried but the surgical removal of hydatid cyst is the only dependable approach to the treatment.
Prevention and control:
Human hydatidosis can be best control by destroying stray population of dogs and regular anticestodal treatment of pets. Food animals act as source of infection for dogs and hence in the slaughter houses infected organ should be disposed off hygienically. Pet owners in endemic areas should be educated to wash the hands before eating to avoid accidental ingestion of eggs of parasite. Vegetables grown in backyards and fields are often contaminated with faces of dogs and hence should not be consumed raw.
- Visceral Larva Migrans (VLM):
It is the condition, arises due to larvae of Toxocara canis, common in children. The adult parasites occur in small intestine of dogs and fox.
Etiology: caused by various species of Toxocara
Mode of transmission: The source of infection is soil contaminated with infective eggs, and the mechanism of transmission is the ingestion of these eggs in contaminated food or water, or via contaminated hands.
Symptoms In humans: Common in children between 1- 5 years of age, Intermittent fever, cough and loss in weight are general symptoms. Ophthalmic involvement is common in children between 4-7 years of age.
Treatment: Diethyl carbamazine with cortisone and higher doses of benzimidazole can be used for treatment.
Prevention and control:
Control of stray cat and dog population. Treatment of dogs, cats and pregnant animals to eliminate to eliminate Toxocara spp. Good sanitation, impervious floor and rat proof conditions in the animal houses. Keeping playgrounds, gardens, beaches, backyards clean and inaccessible to dogs and cats.
- Cutaneous Larva Migrans (CLM):
It is also known as the creeping eruption, dermal larva migrans, ground itch. It is caused due to
larvae of nematode of dogs.
Etiology: the principle etiologic agent is the infective larva of Ancylostoma braziliensis, it’s a
nematode parasite of dogs, cats and other carnivores.
Mode of transmission: the source of infection is infective ancyclomid larvae found in soil. The larvae develop from eggs that are shed in the faces of dogs and cat. Man is infected by contact with contaminated soil.
Symptoms in humans: The infective larva produces a pruriginous (itchy) papule (pus filled space) upon penetration the skin. The larva travels around in the germinal layer and produces sinuous tunnels, and travel few millimetres to several centimetres a day. Scratches leads to pruritis and secondary bacterial infection. The lesions are seen in the exposed parts of the body viz. feet, elbows, buttocks, shoulders and the severity are related to the degree of exposure. Lesions on the palm of the hand or the sole of the foot are particularly painful.
Treatment: oral administration of thiabendazoles, mebendazole and topical application of thiabendazole in water (15%).
Prevention and control:
Control of stray cat and dog population. Dogs and cats should not be allowed on beaches or in places where children play in the sand. The areas susceptible to contamination should be kept dry, clean, and free of vegetation. Maintain personal hygiene.
- Skin diseases:
The most common skin diseases a dog can pass on to people are scabies and ringworm. Both
are very common diseases with obvious symptoms.
Symptoms:
Fig. 1. Lesion caused by dermatophytes Credit: Google (beautyhealthtips.in) |
Ringworm: also termed as dermatophytosis, this disease is caused by a fungus which leads to circular patches on the skin, hairs and nails. Spores from this fungus makes its way into a shared environment, infecting other dogs, other cats and even humans.
Scabies: this is caused by a mite which burrows into the skin producing pruritus (pus) and areas which develop into wounds and cause alopecia (loss of hair). When the mite is in the environment, it can be very contagious especially with young or immunosuppressed dogs. Among the varies species of mites, some of them can also transmit the infection to humans. The most common one in dogs is known as sarcoptic mange and is cause by the mite Sarcoptes scabiei.
Mode of transmission: Direct contact with infected dog.
Fig. 2. Lesion caused by mites in scabies Credit: Google (memoryfoamtalk.com) |
Treatment: Treatment of ring worm includes local application of weak solution of iodine, whitefield ointment etc. Systemic treatment, which includes intravenous injection of sodium iodide, and oral administration of griseofulvin, may prove useful. The treatment of scabies is achieved by local application of various preparation includes permethrin, ivermectin, crotamiton lotion.
Prevention and control:
Preventive measure is to maintain personnel hygiene. Aspiration of areas, disinfection and regular washing of bedding and other material which comes in contact with the dog is vital. It is also important to keep the dog under close observation and take it to the veterinarian when you see any initial symptoms.
Conclusion:
Zoonoses are diseases that involve both humans and animals and can be transmitted either by domestic, pets or by wildlife animals. Many animals and their secretion/excretions can be reservoirs of zoonoses pathogens. Among them, dogs are responsible for the transmission of several zoonotic diseases to their owners. Thus, dog owners should be educated regarding the zoonotic diseases and their ways of transmission to reduce these infections in human population. Several prophylactic and therapeutic strategies have been introduced in order to decrease the zoonotic diseases. Dog owners are recommended to wash their hands after any direct contact with their dogs, their products, urine, or faces to prevent the spread of diseases.
References/ Sources:
A.T. Sherikar, V.N. Bachhil and D.C. Thapliyal, Text book of Elements of Veterinary Public Health By ICAR, New Delhi.
Baneth, G., Thamsborg, S.M., Otranto, D., Guillot, J., Blaga, R., Deplazes, P. and Solano-Gallego, L., 2016. Major parasitic zoonoses associated with dogs and cats in Europe. Journal of comparative pathology, 155(1), pp. S54-S74.
Ghasemzadeh, I. and Namazi, S.H., 2015. Review of bacterial and viral zoonotic infections transmitted by dogs. Journal of medicine and life, 8(Spec Iss 4), p.1.
https://www.who.int/news-room/fact-sheets/detail/rabies
Pan American Health Organization (PAHO). Zoonoses and communicable diseases common to man and animals, PAHO, Third edition (Volume I, II, II).
