Chlamydial, Ricketssial and Parasitic Zoonoses Acquired from Pets
Animals are with human from the beginning of the civilization. In many of the societies they are treated as family members and have right on properties also. Many of us have pets in our close vicinity. They show affections to us and considered as true companion. Moreover they share the living places and even the dinning places. This close attachment may lead to the transmission of many zoonotic diseases which are serious matter of concern not only to public health point of view but also for the survival of pets. These diseases are mainly of parasitic origin and some are of chlamydial and rickettsial origin along with other microbial diseases. To make the life of pet and owner safe it is important to know about them. With this objective the detail of these diseases may be summarized here.Movie All Is Lost (2013)
Chlamydial and Ricketssial Zoonoses
It is a Chlamydial disease which causes conjunctivitis in cats and, less commonly, respiratory symptoms. In humans it can cause pneumonia however, human infection (psittacosis) is generally from parrots and cage birds. There are only isolated cases of Chlamydia being spread from cat to human. Chlamydia psittaci was renamed chlamydophilia felis in 2002, reflecting its role in causing conjunctivitis in cats and its prevalence. However, the old name is still widely used and probably more familiar to doctors and veterinarians. In humans diagnosis of disease begins with the history of exposure to birds and their plumage. The serological testing may be done but it is not very specific.
Rockey Mountain Spotted Fever
Rockey Mountain Spotted Fever (RMSF) is caused by Rickettsia rickettsii. It is transmitted to man through dog tick Dermacentor variabilis bites. The symptoms of disease include headache, chills, general aching, nausea, fever, rash begins from wrist, ankles, palms,
forearms and extend to trunk, neck, face. Dogs are the only non human animal that will show clinical signs of the disease which are similar to those of humans. For the diagnosis of disease clinical signs may be useful but for confirmation isolation of pathogen, serological tests like Weil-Felix and CFT, micro agglutination and indirect immunofluorescence test are of great importance.
Q or querry fever is caused by Coxiella burnetti and is worldwide zoonoses. The occurrence of the Q-fever in India is scanty but serosurveys indicate its wide prevalence of infection both in animals and human beings. The pets such as dogs and cats come in contact of this pathogens remain potential sources of infection to man. The clinical signs resemble with influenza in humans and exhibits sharp rise in temperature, frontal headache and photophobia. For the diagnosis of disease clinical signs are alone sufficient but for confirmation isolation of organism from blood collected during acute phase of the disease or by demonstration of significant increase in the specific antibodies in paired sea samples may be done. For further confirmation serological tests such as CFT, AGT, Luoto’s capillary tube agglutination test, ELISA and indirect immunofluorescence may be tried.
Parasitic Zoonoses acquired from pets
Cryptosporidiosis is a zoonotic disease characterized by enterocolitis and diarrhoea in man and caused by a protozoan Cryptosporidium parvum, C.muris, C.bovis, and C.agni. It is shed in stool of pets and transmitted to humans either through direct contact with stool or via contaminated drinking water. Children and immuno-compromised people are most at risk of contracting Cryptosporidiosis, for example the elderly or AIDS patients. In immune competent individuals the disease is usually restricted to a “flu-like” illness that lasts up to six weeks and is accompanied by diarrhoea and abdominal pain however in immune deficient people the disease can be fatal. For disease diagnosis faecal examination to detect oocytes or immunoblotting, isoenzyme analysis, ELISA, PCR-RFLP can be used for species specific diagnosis. For control of disease high standard hygiene should be maintained and ammonia liberating disinfectants may be used to eliminate the oocytes from the environment.
Giardia intestinalis and G. duodenalis are the flagellates protozoan which are present in the intestinal tract of many domestic, pets and wild animal species and causes a diarrhoeal disease. Infection in humans and animals occurs via ingestion of contaminated water. Giardia sp. is cold tolerant and can survive some chlorination systems. Giardia can also be spread through direct contact, and infected cats and dogs are a high risk zoonotic risk to humans. For the diagnosis of Giardia, its antigen detection may be done by ELISA using monoclonal antibodies. It can also diagnosed by faecal examination for cysts and trophozoites under microscope using SAF and merthiolate-iodine-formaldehyde technique. Good water hygiene is an essential step for its control and prevention.
Hook worm infection
Ancylostoma braziliense, A. caninum, A. tubaeformis are the hookworms capable of infecting the dogs and cats. Their eggs are passed by adult females in dog or cat faeces and hatch larvae on the ground which becomes infective in 1 to 3 weeks. They enter the human beings by broken skin and migrate into lungs via bloodstream. Prevalence of hook worm infection varies from 3-61% in dogs which indicates the enormity and public health importance of disease in India. Disease manifestations includes Loefflers syndrome with larvae in sputum, corneal opacity and eosinophilic enterocolitis may be observed in initial phase but in later stage it shows sudden onset of severe abdominal pain. For the diagnosis of hook worm ELISA and Western blot techniques can be used.
Dipylidium caninum is the tapeworm mainly responsible for the zoonoses in human beings. Its definite hosts are dogs and cats and intermediate host is flea or louse. When this flea or louse of pets infect the human food or get entry in the mouth through oral route then they produce illness in human beings. The disease is mainly asymptomatic in humans. However, sometimes it may exhibits signs like abdominal discomfort, diarrhoea, nausea and weakness. This tapeworm causes depletion of vitamin B12 which may lead to macrocytic hypochromic anaemia. In later stage it produces neurological signs viz. atrophy of tongue, formication of fingers and lower extremities, impairment of tactile sensation. For the diagnosis of the case stool samples may be examined for presence of operculated oval eggs of D. latum.
Toxoplasmosis is widely prevalent zoonotic disease caused by Toxoplasma gondii. Humans are mostly affected by contact with domestic cat faeces. Cats are infected after eating birds, rodents or raw meat containing the intermediate stage of this parasite. The cat then excretes an infective stage in its faeces. Toxoplasma gondii most often causes clinical disease in immunosuppressed people including the elderly, those on immunosuppressive drugs, people with AIDS and in women during the initial 4 months of pregnancy. It can then affect the foetus, and may cause deformities. In people who have previously been infected, the dormant tissue cysts are activated. Stress can also activate dormant cysts. Activated tissue cysts can produce millions of toxoplasmas which can lodge in the heart or brain and other major organs. The disease exhibits signs from mild fever, body pain to fatal encephalitis. For the diagnosis of diseases following techniques may be adopted viz. isolation by mice inoculation, demonstration of parasite antigens in tissues by histopathology or HRPO or FITC antibody conjugate or ELISA, demonstration of antibodies by sabin Feldman Dye test or IHA or CFT or IFA or modified direct agglutination test or ELISA and detection of parasite DNA in tissues by using PCR.Simple hygiene can prevent infection. Avoid contact with potentially contaminated soil infected with cat stool and avoid touching mouth with soil-tainted fingers.
Hydatid disease is caused by the metacestode of Echinococcus granulosus that live in the intestine of dogs. Hydatidosis is one of the most common zoonotic infections in many parts of the world. Humans are accidentally infected with hydatid disease. Hydatid disease in humans is seen as large cysts in various organs particularly affecting the liver followed by lungs and other organs. Its symptoms depend on number, size and location of hydatid cyst in body which starts from allergic, anaphylactic reaction to anaphylactic shock with pulmonary oedema. Diagnosis of hydatid cyst is a difficult task and it is mainly based on clinical signs, radiological and serological methods. Among them radiographic examination is the most reliable technique since it indicates the size and location of cysts. Several serological methods like CFT, IEF, IFA, ELISA and scolex precipitation tests may be tried but they shows the cross reactivity with other metacestodes. Basic hygiene such as washing hands with soap after gardening or touching the dog and washing vegetables that may have been contaminated by dog faeces is important in prevention of this disease. The deworming with albendazole or praziquantel in dogs in every six weeks in rotation will break the life cycle of the parasite and the disease in dogs and humans may be prevented.
Visceral Larval Migrans
Visceral larval migrans primarily affects children and characterized by eosinophilia, hepatomagali, pulmonary infiltration, ophthalmic and nervous involvement. It is caused by a nematode Toxocara canis or T. cati that lives in the intestine of dogs and cats. It is spread to children when they inadvertently eat worm eggs contained in dog or cat faeces. When the animal is patted, worm eggs that are on the pet’s coat may be transferred onto the hands of the child and then into the mouth. These eggs hatch in the child’s intestine and migrate around the body causing internal lesions. In the worst cases, the worms can migrate into and block the artery that supplies blood to the retina of the eye, and in some cases may cause temporary or permanent blindness. For the diagnosis of disease serdiagnostic tests like compliment fixation test (CFT), indirect haemagglutination (IHA) and ELISA are found to be highly specific and sensitive. For the prevention and control of disease personal hygiene and regular deworming of pets with albendazole is highly recommended.
The every disease has its after effects either in the form of direct disease condition or the various associated after effects. The treatment and care of pets needs not only time but also investment. As vaccination is not available for these conditions in pets therefore, extra precautions are to be taken which includes personal hygiene, environmental sanitation, health education, regular deworming and maintaining distance between pets and children.
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