zootonic disease

• Zoonotic disease

  An infectious disease that has jumped from a non-human animal to humans
• Zoonotic pathogens

  • May be bacterial, viral or parasitic, or may involve unconventional agents and can spread to humans through direct contact or through food, water or the environment
• Zoonotic diseases represent a major public health problem around the world due to our close relationship with animals in agriculture, as companions and in the natural environment
• Reasons for the spread of zoonotic diseases

  • Changes in our way of living
  • Climate change
  • Habitat destruction
  • Introduction of alien species – exotic pets
  • Urbanisation
  • Travel
  • Food handling
• Diseases that cross from animals to humans, e.g. HIV, result from increased contact between humans, wildlife and livestock
• As deforestation diminishes biodiversity and infrastructure increases, the risk of pandemics increases
• Ebola Virus Disease (EVD)

  1. People get EVD through direct contact with an infected animal (bat or nonhuman primate) or a sick or dead person infected with Ebola virus

  2. The virus spreads through direct contact (such as through broken skin or mucous membranes in the eyes, nose, or mouth) with blood, body fluids or contaminated objects

  3. Virus may spread through the handling and consumption of wild animal meat or hunted wild animals infected with Ebola
• Tuberculosis

  Two forms - Mycobacterium tuberculosis and Mycobacterium bovis (main source is cattle)
• Mycobacterium bovis has been isolated from numerous wildlife species, including, sheep, goats, horses, pigs, wild boars, deer, dogs, cats, foxes, mink, badgers, and rats
• Bovine TB (Mycobacterium bovis)

  1. Transmitted by contact with infected domestic and wild animals

  2. Indirectly by ingestion of contaminated material

  3. Within cattle usually by inhalation of infected aerosols (coughing)

  4. Calves can be infected by ingesting colostrum or milk from infected cows

  5. Humans can become infected by ingesting raw milk from infected cows, or through contact with infected tissues at abattoirs or butcheries
• The risk of transmission from infected badgers to cattle

  Depends on the prevalence of infection in the badger population, routes and levels of excretion from the infected badgers, and routes of exposure of the cattle
• Transmission from infectious badgers to cattle

  1. Infectious aerosol

  2. Ingestion of food contaminated with infectious badger excreta or wound discharge
• High prevalence of lung lesions and bacterial culture in lungs of badgers and cattle strongly supports infectious aerosols as the primary infection and excretion
• In the UK, badgers are the primary wildlife host implicated in transmitting infection to cattle
• Badgers are covered by the Protection of Badgers Act 1992 (PBA), but have been killed in England since 2013 using Natural England licences which permit culling outside of the main badger breeding season
• The majority of cull areas are the high-risk areas (HRA) for bTB (west and south west of England)
• Culling is carried out to reduce transmission of bTB from badgers to cattle
• Licensed culling within the HRA aims to reduce the badger population by at least 70% over 4 years, and maintain levels with some culling for the next 5 years
• Analysis of the impact of badger culling on bovine tuberculosis in cattle in the high‐risk area of England, 2009–2020 is consistent with a prediction that 'badger culling can make no meaningful contribution to the control of bTB in cattle'
• In the United Kingdom, there have been 149 confirmed cases in humans of highly pathogenic avian influenza (HPAI) H5N1 since 1 October 2022
• Avian influenza or bird flu


  The disease caused by infection with avian (bird) influenza (flu) Type A viruses
• These viruses naturally spread among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species
• Bird flu viruses do not normally infect humans, however, sporadic human infections with bird flu viruses have occurred
• Influenza A viruses


  Endemic in 6 animal species or groups (wild waterfowl, domestic poultry, swine, horses, dogs, and bats) in addition to humans
• Avian influenza A (bird flu) viruses may be transmitted from infected birds to humans and other animals


  1. Via contact with infected birds or environments from exposure to saliva, mucus, or faeces from infected birds via a person's eyes, nose, or mouth, or is inhaled

  2. Through an intermediate host, such as another animal
• More than 60 different wild bird species in the UK have been affected by a strain of the H5N1 avian flu virus
• Since the Spring of 2021, more than 86 million birds in the US and Europe have been killed, mostly as a result of poultry culling to stop the spread of the disease
• The current outbreak is thought to be the worst ever in the UK
• Poultry farmers kept turkeys and chickens inside to prevent and infection and spread to humans
• Malaria


  A serious and sometimes fatal disease caused by a Protozoan carried by the female Anopheles mosquito
• Types of malaria that infect humans

  • Plasmodium falciparum
  • P. vivax
  • P. ovale
  • P. malariae
• P. knowlesi


  A type of malaria that naturally infects macaques in Southeast Asia, also infects humans, causing zoonotic malaria
• Malarial transmission cycle


  Female Anopheles mosquito bites human and injects Plasmodium sp.
• Global warming


  Will extend the geographical range of malaria-transmitting mosquitoes
• Requirements for malaria to become indigenous in the UK

  • Returning travellers with primary infections
  • Appropriate mosquitoes to bite them e.g. A atroparvus
  • Appropriate summer temperatures
  • Completion of intra-mosquito parasite stages such that malaria can be secondarily transmitted to bitten humans
• There must also be a failure of travellers to protect themselves against malaria, suitable UK environments for mosquitoes, and secondary cases to be unrecognised and thus remain untreated and bitten by UK mosquitoes in which Plasmodia become infectious to bitten humans (tertiary cases)
• Lyme disease

  A bacterial infection, caused by Borrelia burgdorferi and rarely, Borrelia mayonii, transmitted to humans through the bite of infected blacklegged (deer) ticks
• There are estimated to be around 3000 cases of Lyme disease diagnosed in England each year
• Ticks are most active in the spring and summer months when the weather warms up but can be found all year round
• Typical symptoms of Lyme disease

  Fever, headache, fatigue, and a characteristic skin rash called erythema migrans