3. Anthrax, tetanus, botulism, and other anaerobic infections

Plan

• Anthrax

• Tetanus

• Botulism

• Botulism in waterfowl

• Botulism in mammals

• Other anaerobic infections

• Enterotoxemia

• Blackleg disease

• Bovine bacillary haemoglobinuria

• Malignant oedema

• Procedures

• Sanitation

  • Application of formaldehyde

Anthrax

AETIO.

Caused by Bacillus anthracis: spore-forming G+.

Causes high mortality mainly in herbivores.

It is WOAH-notifiable.

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EPIZOO.

• Zoonotic

• On all continents except Antartica

  • Endemic areas: South America, Africa, Asia, South Eu

  • Present in Benin, Bangladesh, Equator, Ethiopia, Indonesia, Nepal, Nicaragua, Uganda, Turkey, Uruguay in 2023

  • Present and limited in Azerbaijan, Canada, Spain, Italy, Kazakstan, Kenya, Bhutan, Mongolia, Romania, Russia

  • Present an limited in Burkina Faso, Congo, Kirghizistan, Iraq, Liberia, Mozambique, Nigeria, Sierra Leone, Tanzania, Zambia

• Usually sporadic outbreaks in response to unusual weather (floods) causing dormant spores to come to surface.

• Transmission:

  • Not typically from animal to animal

  • Production of extremely resistant spores on contact w/ oxygen

    • Can survive hundred years in soil

    • Enter host by ingestion or inhalation

  • Carnivores can ingest infected meat

  • Vectors: insects

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PATHO.

1. Entry

2. Spores infect Ma

3. Germination and proliferation

   • Initial lymphadenitis and lymphangitis

     • Local necrosis and extensive oedema

4. Bacteremia

5. Septicaemia

6. Haemorrhages

7. Death

Lethality is due to virulence factors:

• Capsule: against phagocytosis

• Anthrax toxin

  • Protective Ag

  • Oedema factor

  • Lethal factor

The cause of death is lack of O₂.

Forms:

• Skin

  • Blisters surrounding swelling → painless ulcer w/ black centre

• Inhalation

  • Fever, chest pain, shortness of breath

• Intestinal

  • Bloody diarrhoea, abdominal pain, nausea, vomiting

• Injection

  • Fever, abscess at site of inj.

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CS

Usually peracute, acute, or subacute: ante-mortem signs may be absent.

Ru

• Death w/o previous signs

• Acute:

  • High fever, muscle tremors, dyspnoea shortly before death

  • Unclotted blood from openings and no rigor mortis post-mortem

• Subacute:

  • Fever, depression, inappetence, weakness

Horses

• Digestive upset, colic, fever, depression, swelling up to four days before death

Car

• Intestinal form, fever, cramps

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Dx

• Laboratory (in specific lab not clinic or field):

  • Blood: presence of bacteria

    • On tail vein in vivo

    • Sample from ear: peripheral bacteremia

    • 3 layers packaging

  • Identification

    • Culture: BA (non-haemolytic)

    • Ascoli test, PCR: immunology

    • Biological experiment

    • ELISA is not reliable

Tetanus

AETIO.

= Lockjaw

Caused by Clostridium tetani: sporulating G+ anaerobe bacillus.

Production of toxins interfering w/ normal muscle contractions.

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EPIZOO.

• Zoonotic

• WW: especially in warm and humid climates w/ soil rich in organic matter such as Africa, Asia, and USA

• Transmission:

  • Soil, saliva, dust, manure

  • Ingestion, inhalation of spores

  • Cuts, puncture in skin

• Mortality ~ 80%

• Recovered animals do not develop protective immunity

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PATHO.

Spores cannot establish infection in well perfused tissues.

1. Entry of spores

2. Suitable condition if necrosis is present

3. Germination and multiplication

4. Release of neurotoxin when bacteria undergoes autolysis

   • Zinc-binding protease

5. Absorption by motor nerves

6. Retroaxonal transport to spinal cord: asending tetanus

7. Toxin cleaves vesicle-associated membrane protein VAMP/synaptobrevin: no release of acetylcholine by vesicles

8. Spasmodic, tonic contractions of the voluntary muscles

If more toxin is released at infection site than surrounding neurons can take up the excess is carried off by lymph to bloodstream causing infection of CNS: descending tetanus

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CS

• Spasms begin in jaw and progress to the rest of the body

  • Each last few minutes

  • Occur frequently for 3-4 weeks

  • Severe enough to cause fractures

• Fever, sweating, headache, trouble swallowing, high blood pressure, tachycardia

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Dx

• History, CS

• Toxin demonstration in serum

• Gram-stained smears

• Culture from entry wound

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Tx

• Curariform/Neuromuscular -blocking agents OR tranquilizers OR barbiturates sedatives

  +

  Tetanus anti-toxin: in sub-arachnoid space (into CSF)

  • 2-3 weeks passive protection

  • S.C.

• ATBs

Botulism

Severe, often fatal food/wound/infant-borne disease of mammals and birds.

Caused by Clostridium botulinum releasing the botulinum nerotoxin: seven types A-G.

Its is zoonotic.

Listed as a potential biological weapon.

Leads to severe flaccid paralytic diseases in Hu and other animals. It is the most potent toxin known to mankind, natural or synthetic.

Botulism in waterfowl

EPIZOO.

Clostridium is a typical sapro-zoonosis. It is not contagious in that it does not spread from bird to bird; instead it is ingested by maggots that serve as food for waterfowl. These maggots become infected by feeding on substrates and organic matter hosting the toxin.

Prevalence of the toxin increases in summer in warm fishponds and lakes due to anaerobic conditions.

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CS

Intensity depends on the amount of consumed toxin as well as susceptibility.

• Paralysis, paresis: inability to fly and walk

  • Paralysis of neck muscles can result in drowning: “limber neck” / “swan neck”

• Mydriasis

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Dx

• Toxin in serum, crop, GIT

• Neutralisation test

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Prev.

• Cleaning lake bottoms

• Collecting dead animals

Botulism in mammals

EPIZOO.

Mammals and especially dogs and cats are quite resistant to the oral toxin.

But under certain conditions like P deficiency or protein deficiency in Ru they may consume a higher quantity of contaminated meat sources.

Toxico-infectious botulism is the diseases in which C. botulinum grows in tissues of a living animals and produces toxins. They are then liberated from lesion and cause typical botulism.

Sources:

• Decaying carcasses or vegetable material (spoiled silage or hay)

• Contaminated can food in Hu

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PATHO.

1. Entry of germinated spores: ingestion

2. Bloodstream (no nerve transport)

3. Reaches synapses

4. Cleaves neuron MB-associated protein Snap 25: no acetylcholine release

   • Part of the SNARE proteins complex (VAMP, Snap 25, syntaxin) w/ VAMP being vesicle MB protein and Snap 25 and syntaxin being neuron MB proteins

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CS

• Muscle paralysis

  • Progressive motor paralysis

• Disturbed vision

• Difficulties in mastication and swallowing

• Progressive generalised weakness

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Dx

• History: evaluation of environment and feed

• Identification: culture, PCR

• Serology: toxin demonstration by ELISA

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Tx

• Removal of source

• Anti-toxin

• Supportive and symptomatic treatment: guanidine hydrochloride to stimulate Ach release

Other clostridial infections

• C. perfringens

  • Enterotoxemia

  • Gangrene

• C. difficile/spiroforme

  • GIT in lagomorphs/rodents

  • Colitis in Hu

• C. septicum

  • Malignant oedema

• C. chauvoei

  • Clostridial myositis / Blackleg disease in Ru

  • Muscle necrosis in hu

Enterotoxemia

Condition induced by absorption of large volumes of toxins produced by Clostridium perfringens in intestines (production under certain conditions).

There is several strains: A-D. Epsilon toxin produced by strain Type D is the most significant.

Cause damage to intestinal wall, and are responsible for:

• Rapid deterioration of health

• Loss of appetite

• Weight loss

• Listlessness

• Bloody faeces or undigested food in it

Blackleg disease

Highly fatal disease of young cattle caused by Clostridium chauvoei: spore-forming G+ anaerobe rod.

Introduction of spores via intestine → blood → muscles. Spores stay in muscles until anaerobic conditions occur and then germinate and proliferate.

The bacteria produces a large amount of gas as by-product when growing. This gas causes the tissue to make a crackling or popping sound when pressed.

Acute severe lameness and marked depression are common.

Bovine bacillary haemoglobinuria

It is an acute infectious toxaemic disease caused by C. haemolyticum.

It affects cattle primarily but has been found in sheep and rarely in dogs.

After ingestion, spores reach liver and onset depends on anaerobic conditions development: usually in liver fluke Fasciola hepatica infestation. Spores then germinate and the vegetative cells produce ß toxin / phospholipase C.

Leads to intravascular haemolysis → haemolytic anaemia and haemoglobinuria.

Malignant oedema

It is an acute, usually fatal toxaemic disease caused by C. septicum.

Infection via contamination of wounds containing devitalised tissue and debris.

Clostridial toxins cause local and systemic signs: excessive inflammation → oedema → necrosis → gangrene:

• Soft swelling pitting on pressure

• Exudate in subcutaneous and intramuscular CT: dark-brown to black muscle

Extension of CS in case of advanced stage.

Procedures

ANTHRAX

Control

• Suspected cases are reported to state veterinarian → disinfection of premises, vehicles, and others

• Close herd monitoring since animals die quickly

• No opening of carcasses in the field if suspected to avoid dissemination of spores

  • Burning of carcasses

  • Burying at > 2m depth + covered w/ lime

  • Treatment of surrounding contaminated soil

Prev.

• Avoid direct contact w/ infected or suspected animals

• Vaccination

  • Annually

  • In some countries

• Prophylactic ATBs for workers

• Disinfection prior to restocking

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TETANUS

Control

• ATBs and anti-toxins

• Oxygenation of wound

Prev.

• Vaccination

  • Safe, effective, long-term protection

  • Active immunisation w/ tetanus toxoid

    • Another injection after a dangerous wound to increase circulating Ab

  • I.M. on side of the neck

  • Combined w/ anti-toxin: on other side on neck

• Prevention and treatment of wounds

• Disinfection

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BOTULISM

Control

• Removal of sources

• Prevention of contact btw infected and susceptible animals

• Correction of dietary deficiencies

• Proper disposal of carcasses

• Proper home-canning of food: pressure cooking or boiling

Prev.

• Good husbandry

  • Protection of food

  • Removal of decaying grass and spoiled silage

  • Rodent control

  • Disposal of carcasses

  • Prevention of food decaying

• Vaccination

  • In endemic areas

  • In horses, cattle, sheep, goats, minks, pheasants

  • Passive immunisation: anti-serum adapted to toxin present in the region

  • Active immunisation: botulism toxoid

  • Immunisation of cattle w/ Type C and D toxoid in South Africa and Australia

  • Toxoid also used in minks and peasants

Sanitation

ANTHRAX

Spores are extremely resistant and can survive centuries in soil, a year in slurry, and 2 years in milk.

Disinfection:

• Chloramin T (10%)

• NaOH (10%)

• Formalin (10%)

• Peracetic acid (1%)

• Chlorinated lime (10%)

Manure

• Incineration, formaldehyde (10%), glutaraldehyde (4%)

Slurry

• Preliminary disinfection (10% formaldehyde), final disinfection (10% formaldehyde)

Housing

• Fumigation w/ formaldehyde + classic disinfection (above)

Soil

• Flooding w/ disinfection: lime, phosphoric acid, peracetic acid

  • 8-10 l/m², 20 cm

Wounds

• Hydrogen peroxide

The following 3-steps approach is recommended:

1. Preliminary disinfection: 10% formaldehyde, 4% glutaraldehyde

2. All surfaces washed /scrubbed w/ hot water

3. Final disinfection: 10% formaldehyde, 4% glutaraldehyde, 3% hydrogen peroxyde, 1% peracetic acid, 5-10% sodium hypochlorite

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TETANUS

Spores can survive for years in soil, faeces, water, and feed.

Destroyed by:

• Sterilisation: autoclave at 121°C for 15 min OR ionising radiation

• Disinfection: 10% chlorinated lime, 3% formaldehyde

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BOTULISM

Vegetative bacteria is relatively susceptible to many disinfectants: sodium hypochlorite, HCl, ethanol.

Spores are resistant in environment and require autoclaving, gamma radiation, or formaldehyde.

Toxin is inactivated by exposure to sunlight for 1-3 hours OR heating to 80°C for 30 min or 100°C for 10 min.

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CONDITIONS FOR USE OF FORMALDEHYDE FOR DISINFECTION

It is a carcinogenic agents: class 1B carcinogen and class 2 mutagen.

• Sealed room

• Rooms up to 30 m²: 4 l of water + 400 ml of formalin boiled

• Carried out by professionals w/ training

There is no alternative agent to replace currently.

Approved in 2015 as a biocidal active in products intended for disinfection of animal housing, animal feet, veterinary-associated vehicles and eggs w/in hatchery.