Zoonoses | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

• Zoonoses are diseases that can be transmitted from animals to humans. The World Health Organization recognizes approximately 150 significant zoonotic diseases. In the meat industry, preventing diseases and infections that naturally pass from animals to humans is crucial.
• Workers in slaughterhouses are particularly at risk of acquiring specific zoonotic diseases. These diseases are infections that are naturally transmitted between vertebrate animals and humans.

Common Zoonotic Diseases:

• Anthrax:
  • Anthrax is a notifiable disease under public health regulations. Human infection typically occurs through skin wounds, inhalation during wool sorting, or ingestion of contaminated flesh.
  • Various preventive measures can be taken in workplaces like slaughterhouses to reduce the risk of anthrax transmission, such as washing materials thoroughly, using disinfectants, and proper storage.
  • Anthrax can manifest in different forms in humans, including cutaneous, pulmonary, and intestinal forms, each with distinct symptoms and levels of severity.
• Brucellosis:
  • Brucellosis primarily affects individuals handling livestock, carcasses, and related materials. Slaughterhouse workers are especially at risk, particularly when dealing with Brucella reactor animals.
  • Strict hygiene practices are crucial in preventing Brucellosis transmission, including careful handling of animal parts, use of protective gear, and regular handwashing with bactericidal soap.
  • Human infection with Brucella species leads to symptoms like fever with irregular patterns and a tendency to recur. Brucellosis is recognized as an industrial disease, with most cases reported in abattoir workers.

Contagious Pustular Dermatitis

• Contagious pustular dermatitis, also known as orf, commonly affects abattoir workers on hands, wrists, and forearms.
• Caused by a DNA virus from the parapoxvirus genus, it manifests as chronic, raised circular weals on the hands.
• Strict hygiene and prompt treatment for cuts are essential preventive measures.

Erysipelas

• Erysipelas, caused by Erysipelothrix insidiosa, spreads through skin abrasions or ingestion.
• Manifests in various forms including localised cutaneous infections, diffuse skin eruptions, and septicemic forms.
• Predisposing factors like poor housing and sanitation can increase susceptibility.

Leptospirosis

• Leptospirosis, associated with rats and other animals, affects various workers like abattoir workers and veterinary surgeons.
• Hygienic precautions, rat population reduction, and prompt treatment have decreased its risk.
• In pigs, leptospirosis causes a haemolytic type of icterus.

Listeriosis

• Listeriosis, caused by Listeria monocytogenes, can be transmitted through contaminated food.
• Primarily found in temperate regions, it can lead to encephalitis, abortion, and high mortality rates in animals.
• Total condemnation is necessary in cases of listeriosis to prevent spread.

Louping-Ill

• Louping-ill, an acute encephalitis transmitted by ticks, affects abattoir staff through contact with infected animals.
• Arises from ticks carrying the disease from animals to humans, causing significant health risks.

Avian Ornithosis and Psittacosis

• Avian ornithosis and psittacosis, diseases transmissible to humans, are prevalent among birds like parakeets, parrots, and domestic poultry.
• Ducks, turkeys, and pigeons are common sources of human infections.

Psittacosis

• Psittacosis is an infectious disease that can affect individuals more than once. It is typically mild but can also manifest severely. Human transmission occurs through inhalation of infective aerosols or dust contaminated with bird droppings, particularly in settings like poultry farms.
• Chlamydia psittaci, a bacterium in the genus Chlamydia, is responsible for psittacosis. Symptoms in humans include gastrointestinal issues, vomiting, headache, insomnia, and pneumonia. Recovery is usually complete, although convalescence can be prolonged.
• Treatment with tetracyclines and antibiotics is effective, and prophylaxis with chlortetracycline is recommended for disease control. Adequate ventilation, clean environments, and the use of dust masks are essential preventive measures

Q-Fever

• Q-fever is classified as an occupational disease in some regions. It is transmitted through tick bites and inhalation of infected dust, with rare cases of transmission through contaminated milk and meat. Coxiella burnetii, the causative agent, can persist in the environment for extended periods.
• The disease primarily affects ruminant animals like goats, sheep, and cattle, with many wild animals also serving as reservoirs. In humans, Q-fever presents as an acute febrile illness with symptoms like malaise, anorexia, and weakness. Pneumonia is common, with low mortality rates.

Ringworm

• Ringworm is a skin condition caused by a group of fungi called dermatophytes. It can be contracted by individuals handling or slaughtering cattle, especially during winter when animals are more susceptible. Diagnosis involves microscopic examination of affected hairs.
• Infection typically occurs through direct contact with infected animals or indirectly. Ringworm spores can persist on animals' skin without causing lesions, making them potential sources of infection. Maintaining high personal hygiene standards is crucial in preventing the spread of ringworm.

Salmonellos

• Salmonellos is is a highly contagious global disease affecting all animals. Its prevalence is increasing due to factors like intensive livestock systems, poor hygiene practices, and stress in animals. The disease is mainly transmitted through pig and poultry meat.
  Control measures for salmonellosis involve strict attention to hygiene, nutrition, housing, ventilation, rodent control, stockmanship, and the appropriate use of drugs, antibiotics, and vaccines. Preventive measures include providing Salmonella-free food, isolating new livestock, and minimizing stress.

Streptococcal Meningitis

• A disease in pigs caused by Streptococcus suis type-2, leading to meningitis.
• Common among individuals working with pigs, meat industry workers, and veterinarians.
• Symptoms include fever, severe headache, numbness, foot pain, rigors, and erythema.
• Responds well to antibiotic treatment over several days.
• Control measures involve maintaining high personal and environmental hygiene standards, wearing gloves, and prompt wound care

Tularaemia

• Can be acquired through infected hares, rabbits, sheep, contaminated dust, water, tick and mosquito bites.
  Workers in various occupations like agriculture, wool shearing, and fur trapping may be at risk.
• Manifests in glandular or ulcero-glandular form, and less commonly in typhoidal and pneumonic form.
  Symptoms include papule at the infection site, lymphadenitis, fever, headache, and muscular pain.
  Responds well to streptomycin, tetracycline, or chloramphenicol treatment.

Tuberculosis

• Caused by Mycobacterium bovis, characterized by the development of tubercles in various organs.
• Progressive disease affecting multiple species.

•  It poses public health risks and affects animal production efficiency, especially in indoor settings during winter.

• Incidence and Spread

  In cattle, Mycobacterium bovis is the causative agent, while Mycobacterium avium affects birds, and Mycobacterium tuberculosis affects humans. Transmission occurs through various excretions from infected animals such as sputum, feces, and milk, with inhalation or ingestion being common routes.

• Transmission and Pathogenesis

  The disease spreads through two stages: primary complex and post-primary dissemination. Symptoms include emaciation, capricious appetite, cough, dyspnea, and lymph node enlargement. Tuberculosis mastitis is a significant concern due to public health risks and challenges in diagnosis.

• Diagnosis and Control

  Diagnosis involves palpation of supramammary lymph nodes. The disease can be transmitted through infected milk, and pasteurization helps in reducing the risk. Complete eradication is crucial for farmer and public safety.

Zoonoses Overview

• Zoonoses - Definition

  Zoonoses refer to diseases that affect animals and can be transmitted to humans. This transmission can occur commonly or incidentally. For example, diseases like Leishmaniasis, Trypanosomiasis, and malaria, all initially animal diseases, have become prevalent in humans.

• Classification of Zoonoses

  • I. Zoonoses based on the type of lifecycle of the infectious organism The lifecycles of organisms infecting vertebrates fall into four main types, determined by where the infectious organism multiplies or undergoes essential development:
    • 1. Direct Zoonoses: Cycles that require only one vertebrate host species for completion, with a single reservoir or developmental site.
    • 2. Cyclozoonoses: Cycles that involve more than one vertebrate host species for completion.
    • 3. Metazoonoses: Cycles that need both vertebrate and invertebrate species.
    • 4. Saprozoonoses: Cycles requiring both a vertebrate host species and a non-animal reservoir or developmental site for completion.

Classification of Zoonoses

• Based on the nature of the reservoir hosts:
• Anthropozoonoses: Zoonotic diseases maintained by lower vertebrates, e.g., brucellosis, anthrax.
• Zooanthroponoses: Zoonotic diseases maintained in nature by humans, e.g., amoebiasis.
• Amphizoonoses: Zoonotic diseases perpetuated in nature by both humans and lower vertebrates, e.g., staphylococcosis.
• Based on the etiological agent:
• Bacterial Zoonoses: Diseases caused by bacteria like anthrax and brucellosis.
• Viral Zoonoses
• Fungal Zoonoses
• Protozoal Zoonoses
• Nematode Zoonoses
• Arthropod Zoonoses
• Cestode Zoonoses
• Rickettsial Zoonoses

Zoonotic Diseases and Reservoir Hosts

• Domestic vertebrates such as dogs, pigs, chickens, cows, sheep, buffalo, yak, llamas, and goats play a significant role in the transmission of zoonotic diseases.
• Dogs are associated with hydatid disease and coenurosis.
• Swine are linked to taeniasis and cysticercosis.
• Cattle are reservoirs for cowpox, vesicular stomatitis, anthrax, and brucellosis.
• Fowl can transmit salmonellosis, Newcastle disease, and psittacosis-ornithosis.
• Sheep can spread contagious ecthyma and pasteurellosis.

Occupational Zoonotic Diseases

• Slaughterhouse workers face occupational hazards, with the most common risks being injuries from machinery and knives.
• Knife-related injuries, including cuts and abrasions, are prevalent, often leading to sepsis and arthritis if not promptly treated.
• Proper knife design, handle guards, and protection for hands are crucial to prevent injuries.
• A light, cut-resistant glove made of aramid and nylon with a steel core is available to protect workers.

Other Zoonotic Diseases

• Various zoonotic diseases are transmitted by wild mammals and birds, including ringworm, amoebiasis, trichinosis, scabies, fascioliasis, and Q-fever.

Role of Wild Mammals and Birds in Zoonotic Diseases

Introduction

• Wild mammals and birds play a significant role in the prevalence and transmission of zoonotic diseases.

Zoonotic Infections in Wild Hosts

• Some zoonotic infections cause apparent diseases in wild hosts, while many infections in domestic animals and humans remain silent in wild species.
• Wild rats, monkeys, and mice, although not domesticated, are attracted to human habitats and can harbor infections.

Direct Transmission to Humans

• A few wild animal species like rabid bats, foxes, wolves, and animals used as food can transmit infections directly to humans.

Reservoir Hosts of Arthropod-Borne Infections

• Wild mammals like monkeys can act as reservoirs for diseases such as Kyasanur forest disease, Venezuelan equine encephalomyelitis, and various viruses.
• Small mammals also play a role in hosting arthropod-borne infections like tick fever and encephalitis.

Role of Migratory Birds

• Migratory birds contribute to the spread of ectoparasites and zoonotic infections across continents.
• They have been linked to the dissemination of diseases like tick typhus, Q-fever, and tularemia.

Transmission to Domestic Animals

• In various parts of the world, diseases can be transmitted from wild to domestic animals, impacting livestock like cattle.

Risk to Humans

• Workers in the meat industry, especially in slaughtering sectors, face a heightened risk of acquiring zoonotic diseases like anthrax, brucellosis, and tuberculosis.
• Proper safety measures and hygiene practices are essential to prevent the spread of infections in meat processing facilities.