Lecture 35: Infections of hemolymphatic system - III

Anthrax (Woolsorters’ disease, Ragpickers’ disease, Splenic fever, Malignant pustule, Bacillus anthracis Malignant edema),

Anthrax is a serious ___ disease

zoonotic

Anthrax affects what species?

Most mammals and several species of birds, but is particularly important in herbivores

What is the causative agent that causes Anthrax?

Bacillus anthracis

Characteristics of Bacillus anthracis

Gram-positive, large rod, non-motile, endospore forming

“Medusa head” on blood agar

What is important about the vegetative forms B.anthracis?

They are more "fragile" than the vegetative forms of other Bacillus species (die in water or milk)

B. anthracis is dependent on sporulation for species survival making it an

obligate pathogen

What does sporulation require?

A nutrient poor environment and the presence of free oxygen

What is the predominant phase Bacillus anthracis in the environment?

The spore form.

Can survive for decades in soil

What is important about the spore form of B. anthracis?

Markedly resistant to biological extremes of heat, cold, pH, desiccation, and chemicals (and thus to disinfection)

Can B. anthracis spores be produced in the unopened carcass?

No

So, no post-mortem

Transmission of Anthrax in humans is caused by

Cutaneous

Inhalational

Gastrointestinal

Where is Anthrax bacteria present in

Present in hemorrhagic exudate from mouth, nose, anus

Soil

Spores viable for decades!

What are the forms of transmission for Anthrax in animals?

Ingestion

Inhalation

Mechanical (Insects)

What is the MOST common transmission of Anthrax in animals?

Ingestion

Herbivores - contaminated soil

Carnivores - contaminated meat

Where in the US is anthrax sometimes endemic?

Western US

Anthrax outbreaks are often associated with

alkaline soil

What species of animal is primarily affected by Anthrax?

Cattle

The virulence factors of B. anthracis derives from

Presence of a capsule and the ability to produce a complex toxin

Antigenic components of B. anthracis

Protective antigen (PA) – helps toxins enter cells

Edema factor (EF) – causes fluid accumulation (edema)

Lethal factor (LF) – disrupts cell signaling → cell death

Both virulence factors of B. anthracis are encoded by

plasmids and are required for disease production

What is the expression of Anthrax virulence factors regulated by

Host temperature and carbon dioxide

The capsule of Anthrax is composed of

poly-D-glutamic acid and inhibits phagocytosis

Protective antigen of anthrax acts as

The binding moiety for both edema factors and lethal factor

Edema factor of anthrax is an

adenylate cyclase which upsets water homeostasis and has a role in absence of rigor mortis and inhibition of platelet aggregation

Lethal factor of anthrax is a

zinc metalloprotease and is essential for the lethal effects of the toxin, and inhibition of platelet aggregation

The cutaneous form of anthrax in humans accounts for how many cases globally?

95%

Incubation period of anthrax in humans

2 to 3 days

Order of anthrax development in humans

Papule→ Vesicle→ Ulcer→ Eschar

The eschar caused by Anthrax may be surrounded by

Moderate to severe non pitting, gelatinous edema

If left untreated, the case fatality rate for Anthrax in humans is

5 to 20%

Cutaneous anthrax in humans

Incubation period of Gastrointestinal Anthrax

2 to 5 days

Case fatality rate of Gastrointestinal Anthrax

25 to 75%

GI anthrax is __ in the US

rare

What can cause Gastrointestinal Anthrax.

Consumption of undercooked or contaminated meat

Leads to severe gastroenteritis

Incubation period of Inhalation Anthrax

1 to 7 days

Initial phase of Inhalation Anthrax includes

Nonspecific (mild fever, malaise)

Second phase of Inhalation Anthrax includes

Severe respiratory distress

Dyspnea, stridor, cyanosis, mediastinal widening, death in 24 to 36 hours

Case fatality rate of Inhalation Anthrax (untreated)

75-90%

Anthrax treatment in humans

Penicillin

Ciprofloxacin

Doxycycline

Course of treatment: 60 days

Antibiotic treatment of anthrax is only effective in what stage?

Vegetative stage

Prevention and Control of Anthrax in Humans

By preventing disease in animals

Improved industry standards – decreased occupational hazard

Safety practices in laboratories

US human anthrax vaccines is

cell-free filtrate produced from an avirulent strain; it contains no whole bacteria, dead or alive

Who is anthrax vaccine mandatory for

Designated military and emergency-essential personnel, as well as comparable Department of Defense civil employees

Which species is at greatest risk of Anthrax

Ruminants

What are the 3 forms of anthrax in animals

Per-acute: Ruminants (cattle, sheep, goats, antelope)

Acute: Ruminants and equine

Subacute-chronic: Swine, dogs, cats

Pre-acute anthrax in ruminants leads to

sudden death

Signs of Acute Anthrax in ruminants

Tremors, dyspnea

Bloody discharge from body orifices

Chronic (rare) form of Anthrax in ruminants

Pharyngeal and lingual edema

Death from asphyxiation

Acute Anthrax in Equines

Fever, anorexia, colic, bloody diarrhea

Swelling in neck

• Dyspnea

• Death from asphyxiation

Death in 1 to 3 days

How can equines get Anthrax

Insect bite

o Hot, painful swelling at site

Anthrax in pigs causes

Septicemia and sudden death

Pigs with Anthrax have mild subacute to chronic infections characterized by

localized swelling and systemic signs, such as fever and enlarged lymph nodes

Dogs and cats can be relatively __ to anthrax

resistant

Transmitted by Ingestion of contaminated raw meat

Signs of Subacute to chronic Anthrax in Dogs and Cats

Fever, anorexia, weakness

Necrosis and edema of upper GI tract

Lymphadenopathy and edema of head and neck

Death - due to asphyxiation, toxemia, septicemia

What is not advised for animals who died from Anthrax?

Necropsy not advised!

Aka do not open carcass

Treatment of Anthrax

Penicillin, tetracyclines

Is Anthrax a reportable disease?

YES

In livestock, anthrax can be controlled largely by

Annual vaccination of all grazing animals in the endemic area

The anthrax vaccine produced in the US is licensed for use in

livestock only (cattle, sheep, horses, goats, and swine)

What type of vaccine is used almost universally for livestock immunization?

The nonencapsulated Sterne-strain vaccine