Introduction

Anthrax is a zoonotic disease caused by the bacterium Bacillus anthracis. It affects both humans and animals, posing significant threats to public health, livestock industries and wildlife conservation. Understanding the intricacies of anthrax, including its transmission, symptoms and signs in animals and preventive strategies is crucial for managing and mitigating its impact. This article explores the risks associated with anthrax in animals, the symptoms exhibited by infected animals and the measures that can be taken to prevent and control this disease.

Risks of anthrax in animals

Modes of transmission

Anthrax primarily spreads through spores that can remain viable in the environment for decades. The primary modes of transmission include inhalation, ingestion and direct contact with infected materials.

Inhalation

Animals can inhale anthrax spores present in dust or aerosols, especially during dry seasons when soil particles become airborne. Inhalation is particularly dangerous as it can lead to rapid and severe forms of the disease.

Ingestion 

This is the most common route of infection for herbivores. Animals may ingest spores while grazing on contaminated land or consuming contaminated water and feed. Carcasses of animals that have died from anthrax can also contaminate the environment, perpetuating the cycle of infection.¹

Direct contact

Although less common, direct contact with infected animals or their products (e.g. wool, hair and hides) can also lead to infection. Veterinary and agricultural workers are at higher risk due to their close contact with potentially infected animals.²

Environmental factors 

Certain environmental conditions favour the survival and proliferation of Bacillus anthracis spores. Soil characteristics such as pH, organic matter content and calcium levels can influence the persistence of spores in the environment. Alkaline soils with high organic content provide an optimal environment for spore longevity.

Climatic conditions also play a significant role. Droughts can cause animals to graze closer to the ground where spores are concentrated, while heavy rains can lead to surface runoff, spreading spores over larger areas. Floods can bring buried spores to the surface, increasing the likelihood of exposure.³

High-risk animals

Different animal species exhibit varying levels of susceptibility to anthrax.

Livestock 

Cattle, sheep and goats are highly susceptible to anthrax. Infected livestock can experience sudden death, often with little warning. The rapid progression of the disease in these animals underscores the need for vigilant monitoring and immediate intervention.⁴

Wildlife 

Wildlife species such as deer, antelope and other herbivores are also at risk, particularly in regions where anthrax is endemic. Outbreaks in wildlife populations can have devastating ecological consequences and can serve as a reservoir for further transmission to livestock and humans.⁵

Domestic pets 

While rare, domestic pets such as dogs and cats can contract anthrax, usually through ingestion of contaminated meat or contact with infected animals. Although they are less susceptible than livestock, the potential for infection exists, particularly in areas with known outbreaks.⁶

Symptoms of anthrax in animals

The clinical presentation of anthrax in animals varies depending on the form of the disease: peracute, acute, or subacute to chronic.

Peracute form

The peracute form of anthrax is characterized by sudden death, often with little to no preceding symptoms. This form is most commonly seen in herbivores like cattle and sheep.

Sudden death: Animals may die suddenly within hours of infection. This rapid progression leaves little time for intervention, highlighting the importance of preventive measures.

Post-mortem signs: After death, affected animals may exhibit rapid bloating and exude bloody discharge from natural body orifices such as the mouth, nose and anus. The presence of unclotted blood is a key indicator of anthrax.⁷

Acute form

The acute form of anthrax presents with more recognizable symptoms, allowing for potential diagnosis and treatment.

Fever and excitement: Infected animals may exhibit a sudden rise in body temperature and increased excitability or restlessness.

Respiratory distress: Difficulty breathing, staggering, and convulsions are common as the disease progresses. The respiratory distress is often due to swelling and haemorrhaging in the throat and lungs.

Collapse and death: Without prompt treatment, animals typically collapse and die within a few days of symptom onset. The rapid decline emphasizes the need for early detection and intervention.⁸

Subacute to chronic form

The subacute to chronic form is less common but can occur in some animals, particularly those that are partially resistant or have been exposed to a lower dose of spores.

Fever and anorexia: Affected animals may have a prolonged fever and lose their appetite, leading to weight loss and weakness.

Swelling in neck and throat: Swelling in the throat (pharyngeal anthrax) can cause difficulty swallowing and breathing. This form is particularly noticeable in cattle and horses.

Possible recovery: With appropriate antibiotic treatment, animals with the subacute to a chronic form of anthrax may recover. However, early detection and intervention are critical to improve the chances of survival.⁹

Prevention measures

Preventing anthrax in animals involves a combination of vaccination, biosecurity measures, environmental management, and surveillance.

Vaccination

Vaccination is the most effective method for preventing anthrax in livestock and high-risk wildlife populations.

Importance and effectiveness: vaccines stimulate the immune system to recognize and combat Bacillus anthracis. They are highly effective in preventing outbreaks, particularly in endemic areas.

Recommended vaccination schedules: Vaccination schedules vary based on local risk factors and animal species. Typically, livestock in high-risk areas are vaccinated annually. In the case of an outbreak, emergency vaccination programs may be implemented to control the spread.¹⁰

Biosecurity measures

Implementing strict biosecurity measures is essential to prevent the spread of anthrax.

Proper disposal of carcasses: Infected carcasses should be promptly disposed of through incineration or deep burial to prevent environmental contamination. Proper disposal methods are crucial to breaking the cycle of transmission.

Quarantine protocols: Quarantining infected and exposed animals can help prevent the spread of anthrax. Farms and areas with confirmed cases should implement quarantine measures to contain the outbreak.¹¹

Environmental management

Managing the environment to reduce the risk of anthrax exposure is a key preventive strategy.

Control of grazing areas: Rotational grazing and avoiding known contaminated areas can help reduce the risk of exposure to anthrax spores. Ensuring that animals graze on higher ground, away from low-lying areas prone to flooding, can also be beneficial.

Soil treatment and decontamination: Treating contaminated soil with disinfectants or chemicals can reduce spore viability. However, this method is often limited to specific, high-risk areas due to practical and environmental considerations.¹²

Surveillance and early detection

Ongoing surveillance and early detection are critical components of anthrax prevention and control.

Monitoring of high-risk areas: Regular monitoring of livestock and wildlife in endemic regions can help identify and respond to anthrax outbreaks promptly. Surveillance programs should include routine testing of soil, water and animals.

Reporting and responding to outbreaks: Rapid reporting and response to suspected cases of anthrax are essential to contain the disease. Veterinary and public health authorities should work together to implement control measures and prevent further spread.¹³

FAQs

What are the symptoms of anthrax in animals?

Symptoms of anthrax in animals include increased restlessness and excitability, trembling, increased bodily temperatures and resulting fever, spasm of muscles, shortness of breath and walking, moving and standing unsteadily.

How can anthrax be prevented in animals?

Vaccination frequently, monitoring reservoirs of anthrax spores to limit anthrax exposure to farm/wild animals, safe disposal of animal carcasses infected with anthrax and decontamination and cleaning of areas thoroughly can prevent anthrax in animals.

Summary

Anthrax in animals poses significant risks to public health, livestock industries, and wildlife conservation. Understanding the modes of transmission, environmental factors, and high-risk animals is crucial for effective management and prevention.

Recognizing the symptoms of anthrax and implementing preventive measures, including vaccination, biosecurity, environmental management, and surveillance, are key to controlling this deadly disease. Vigilance and preparedness are essential to protect both animal and human populations from the devastating impacts of anthrax.