Livestock diseases - Introduction

27-31 March 2023

Julien Arino (julien.arino@umanitoba.ca)

Department of Mathematics & Data Science Nexus
University of Manitoba*

Canadian Centre for Disease Modelling
NSERC-PHAC EID Modelling Consortium (CANMOD, MfPH, OMNI/RÉUNIS)

Livestock diseases

Theme 2 in Part II of the OMNI/RÉUNIS course

Outline

• Animal diseases, zoonoses and epizootics
• Diseases of livestock
• Examples (from local to global)
  • Scrapie
  • Hoof and mouth disease
  • Bovine tuberculosis
  • Avian influenza

Animal diseases, zoonoses and epizootics

Animal diseases

WOAH (World Organisation for Animal Health - changed May 2022 from former OIE) has 117 Listed diseases, several emerging diseases and additional important diseases (not Listed) and more than 50 wildlife diseases which may have a serious impact on livestock health and public health and can adversely affect wildlife conservation

Animal disease

From chatGPT (emphasis mine)

An animal disease refers to any illness, infection, or health condition that affects animals, whether domesticated or wild. Animal diseases can be caused by a wide range of agents such as viruses, bacteria, fungi, parasites, and toxins. These diseases can affect various body systems, including respiratory, gastrointestinal, nervous, and immune systems, among others. Animal diseases can have significant impacts on animal health, welfare, and productivity, as well as on public health and the economy. Some examples of animal diseases include foot-and-mouth disease, bovine tuberculosis, brucellosis, and African swine fever, among many others

Zoonoses

From the CDC

caused by germs that spread between animals and people

From the WHO

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

Continuing with WHO

[zoonoses] 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. Zoonoses can also cause disruptions in the production and trade of animal products for food and other usess

From ChatGPT (emphasis mine)

A zoonosis, also known as zoonotic disease, is an infectious disease that can be transmitted from animals to humans, either directly or indirectly. These diseases can be caused by viruses, bacteria, parasites, and fungi, and can be transmitted through various routes such as bites, scratches, consumption of contaminated food or water, inhalation of droplets, or contact with infected bodily fluids. Some well-known zoonotic diseases include rabies, Lyme disease, salmonellosis, and avian influenza. Zoonoses can pose significant public health challenges as they can potentially lead to widespread outbreaks and pandemics

“Taylor et al. (2001) documented that 61% of all human pathogens are zoonotic. And of the 175 newly emerging pathogens in humans, 75% are listed as zoonotic … However, it is also important to remember that some diseases affect animals only, often with economic, environmental and/or societal implications.” – Bender et al., Recent Animal Disease Outbreaks and their Impact on Human Populations. 2006: 133

Epizootics

Epizooty refers to a sudden outbreak or occurrence of a highly contagious and widespread disease affecting animals in a particular geographic area or population. It is essentially an animal equivalent of an epidemic. Epizooties are caused by a variety of infectious agents such as bacteria, viruses, fungi, and parasites, and can affect various animal species, including livestock, poultry, wildlife, and companion animals. Epizooties can cause significant economic losses in the affected areas, as they can lead to massive mortalities, reduced productivity, trade restrictions, and increased costs for disease control measures. Some examples of epizooties include avian influenza, foot-and-mouth disease, and African swine fever

Diseases of livestock

Important for several reasons

• Economic consequences
• Consequences on food availability
• Transmission to humans

See, e.g., this report (and here)

AI: Avian influenza

TSE: Transmissible spongiform encephalopathies or prion diseases

Q fever: Q fever is a disease caused by the bacteria Coxiella burnetii

Examples (from local to global)

In the following, we look at several diseases of livestock

All have potential global implications, but the scale of most transmission events ranges from local to global

Example - Scrapie

Scrapie

Transmissible spongiform encephalopathy (similar to BSE) of sheep and goats

Fatal degenerative disease affecting the nervous system

Name derived from one of the clinical signs of the condition: affected animals compulsively scrape off their fleeces against rocks, trees or fences

Other clinical signs include excessive lip smacking, altered gaits and convulsive collapse

Example - Foot-and-mouth disease

( hoof-and-mouth disease, hand-foot-and-mouth disease)

FMD-HMD

Severe, highly communicable viral disease of cattle and swine

Also affects sheep, goats, deer and other cloven-hoofed ruminants. Horses not affected

Elephants, hedgehogs and some rodents also susceptible but do not develop clinical signs of the disease

Fever and blister-like sores on the tongue and lips, in the mouth, on the teats and between the hooves

Many affected animals recover, but the disease leaves them weakened and debilitated

2001 United Kingdom foot-and-mouth outbreak

• 2,000 cases of the disease in farms across most of the British countryside

• Over 6 million cows and sheep were killed to control the disease

• Ministry of Agriculture, Fisheries and Food (MAFF)adopted a policy of "contiguous cull" – all sheep within 3 kilometres (3,000 m) of known cases slaughtered

Example - Bovine tuberculosis

Bovine tuberculosis (bTB)

Chronic contagious bacterial disease of livestock and occasionally other species of mammals, resulting from infection with Mycobacterium bovis (M. bovis)

Bacteria may lie dormant in an infected animal for years without causing clinical signs or progressive disease symptoms

It can reactivate during periods of stress or in older animals

In countries with eradication programs, e.g., Canada, advanced disease is rare as most cases are detected at an early stage and few infections progress to clinical signs

Infected animals with progressive disease shed the bacteria in respiratory secretions and aerosols, feces, milk, and sometimes in urine, vaginal secretions, or semen

Movement of infected animals from one herd to another with subsequent extended close contact increases transmission risk

Where infected wildlife are a reservoir of disease, there is potential for transmission to livestock

Bovine TB in Canada

Reportable disease, suspect cases must be reported to CFIA; CFIA conducts investigation to determine if the disease present

If bovine TB is confirmed, CFIA alerts provincial health department and implements strict disease eradication measures to eliminate the infection and prevent further spread to livestock, humans, and wildlife

Bovine TB control measures in Canada

• Implement a quarantine and restricting the movement of animals and equipment
• Humane destruction of all infected and susceptible exposed animals
• Cleaning and disinfection of infected premises and equipment
• Investigation and testing of all at-risk livestock herds which are epidemiologically associated with the infected premises (tracing)
• Testing livestock and wildlife within a surveillance zone surrounding the infected premises
• Testing any livestock herds that are re-stocked onto a premises where bovine TB was previously confirmed.

A global issue

Forty-four percent of countries reported bovine tuberculosis (bTB) via the OIE World Animal Health Information System (WAHIS) between January 2017 and June 2018

Only a quarter of the affected countries were applying all the relevant control measures

10 goals for zoonotic TB

1. Collect and report more complete and accurate data from human and animal populations
2. Improve diagnosis in people
3. Address research gaps
4. Ensure safer food
5. Improve animal health
6. Reduce the risk to people
7. Increase awareness, engagement and collaboration
8. Develop policies and guidelines
9. Implement joint interventions
10. Advocate for investment

Example - Avian influenza

Avian influenza

Caused by Influenza A virus

Adapted to birds but can also stably adapt and sustain P2P transmission

High pathogenicity avian influenza (HPAI)

• HPAI A virus subtype H5N1: emerging avian influenza virus causing global concern as a potential pandemic threat

• H5N1 has killed millions of poultry throughout Asia, Europe, and Africa

• Coexistence of human flu viruses and avian flu viruses (especially H5N1) will provide an opportunity for genetic material to be exchanged between species-specific viruses, possibly creating a new virulent influenza strain that is easily transmissible and lethal to humans

• CFR for humans with H5N1 is 60%

• AI global concern because it involves multiple bird species, both wild and livestock

• The thing with wild birds is that they fly... :)

See (in French) here:

• Epizooty from August 2021 to May 2022
• "À la mi-octobre 2022, environ 21,8 millions d'animaux (palmipèdes et volailles) avaient été abattus en France dans le cadre de la gestion de la crise (août 2021-mai 2022)"
• "À la date du 23 juin 2022, la France comptait 1 378 foyers d’influenza aviaire hautement pathogène (IAHP) en élevage, 72 cas en faune sauvage et 35 cas en basse-cours"

In conclusion

Diseases of livestock

• are widespread and attack
  • highly organised "food production systems"
  • more traditional food production systems as well
• threaten the livelihood of many
• threaten food security
• have potential pathogenic consequences in humans