Protect Your Livestock: Understanding Anthrax (Splenic Fever) in Cattle, Goats, and Sheep

Anthrax, or splenic fever, is a highly contagious disease that affects livestock globally. The name "splenic fever" comes from the disease's hallmark symptom, which is an extensive enlargement of the spleen (splenomegaly) caused by the infection. Almost all food animals are susceptible to anthrax.

In cattle and sheep with acute anthrax, there is a sudden onset of fever and excitement, followed by lethargy, stupor, respiratory or cardiac distress, staggering, seizures, and eventually death.

The disease is characterized by septicemia, which leads to sudden death and the exudation of tarry blood from the animal's body orifices.

High fever and blood around the nose, mouth, and anus of the carcasses may be present before death, but these signs are not always present, making a diagnosis of anthrax disease difficult.

A postmortem examination is critical, and the absence of blood clotting, the lack of rigor mortis, and the presence of splenomegaly are the most important findings.

Anthrax is the only disease that requires the death of its host to propagate. Although it affects all animals, cattle, sheep, goats, pigs, horses, and humans are particularly vulnerable, while carnivores are more resistant, and birds rarely contract the disease.

Causes of Anthrax Disease

Anthrax is a disease caused by a spore-forming bacterium called Bacillus anthracis. This microorganism is rod-shaped, grain-positive, and has the ability to form spores that are highly resistant.

The resistant spores can withstand dry heat at 165°C for one hour, moist heat at 100℃ for 5 minutes, and are highly resistant to standard disinfectants.

While carnivores are more resistant to anthrax, herbivorous animals are highly susceptible to the disease.

Spores of Bacillus anthracis can remain infective for 10-20 years in soil and pasture. It is known that Bacillus anthracis can remain viable and infective in soil for up to 60 years when stored in a rubber-stoppered bottle.

When the bacillus releases a toxin, it causes edema and damages tissues, which can lead to secondary shock and acute failure.

Transmission of Anthrax Disease

Splenic fever is transmitted through the ingestion of materials that contain spores or virulent bacilli, and biting flies can infect animals. The primary source of infection comes from the carcasses of animals that have died from the disease, as they are likely to be eaten by other animals.

When an infected carcass is opened, the soil around it becomes heavily contaminated with spores. If the carcass remains unopened, the bacilli are protected from exposure to air, and spores do not form easily, resulting in rapid destruction through putrefaction.

Predisposing factors that increase the likelihood of infection include animals feeding on thorny scrub or hard plant material, which can cause injury to the mucous membrane - the entry point for these spores into the bloodstream. Additionally, congregation around water points can be heavily infected, especially after heavy rains following a dry spell when forage is grown on infected soil.

The disease can also spread through meat, bone meal, hides, bones, hair, and hooves, which can introduce the disease to other areas. While the inhalation route is not important in animals, in humans, wool sorters disease can occur after the inhalation of spores. Cutaneous anthrax is more common in humans.

Signs and Symptoms of Anthrax Disease

Cattle, sheep, and goats can exhibit clinical signs of paracute anthrax, such as staggering, trembling, breathing difficulty, convulsions, and rapid death. The disease progresses quickly, and premonitory signs may go unnoticed, with animals often found dead, bloated, and without rigor mortis. In cattle, the incubation period is uncertain but may be between 1-2 weeks.

In the paracute form, death can occur within 1-2 hours without prior signs, showing high fever, muscle tremors, and mucosal congestion leading to collapse, convulsions, and death with bloody discharges from natural orifices.

In the acute form, which lasts for 2 days, animals may exhibit extreme listlessness, very high temperature (42°C), reddened and hemorrhagic mucosae, and sometimes dysentery or diarrhea.

Other symptoms include rapid respiration, high heart rate, anorexia, abortion in pregnant animals, and edematous lesions in the throat, sternum, perineum, and flanks.

The general symptoms of anthrax (splenic fever) include staggering, trembling, difficulty breathing, convulsions, and death.

Note: Progression of the disease is rapid and premonitory signs may go unnoticed; often animals are found dead, bloated, and without rigor mortis.

Postmortem Findings of Anthrax Disease

The carcass undergoes gaseous decomposition, and as a result, all-natural orifices exude dark, tarry blood that does not clot. Putrefaction and bloating occur rapidly, and there is the presence of ecchymotic hemorrhages throughout the body tissues. Additionally, there is the presence of blood-stained serous fluids in the body cavities. Severe enteritis and gross enlargement of the spleen, with softening and liquefaction of its structure, are also observed.

Diagnosis of Anthrax Disease

In cases of sudden animal death, especially in areas where disease outbreaks have previously occurred, laboratory examination of stained smears is recommended, provided the smears are taken immediately after death before putrefactive organisms enter the bloodstream. The Ascoli precipitin test can often confirm the presence of anthrax.

Differential Diagnosis of Anthrax Disease

The differential diagnosis of Anthrax disease can be challenging due to the various possible causes of sudden death. However, by considering the animal's history, we can identify certain characteristics that may be indicative of Anthrax. These characteristics include a history of lightning storms, parachute black legs affecting only young animals, and crepitating swelling.

Other potential causes of sudden death in animals include Acute Leptospirosis, which may occur sporadically and be accompanied by hemoglobinuria. Paracute Leptospirosis may lead to poisoning and hypomagnesemia tetany, along with nervous signs. Acute bloat is another potential cause, which is characterized by the absence of tarry red stool. Finally, Snakebite may be identified by the presence of local swelling and fang marks.

How Do We Treat Anthrax Disease in Livestock?

Managing anthrax in livestock involves several steps. First, the affected herd must be quarantined, and if possible, removed from the contaminated pasture.

Additionally, healthy livestock should be vaccinated, and those showing clinical signs of disease should be treated with antibiotics. Contaminated carcasses should be disposed off, preferably by burning, and bedding should be incinerated.

When large animals such as cattle, goats, sheep, horses, or swine are affected by anthrax, antibiotics such as penicillin and oxytetracycline are commonly used for treatment.

For smaller animals, including pets, amoxicillin, doxycycline, and enrofloxacin have been recommended. However, the effectiveness of these antibiotics is not well documented, and it is best to consult with a veterinarian for appropriate treatment.

Note: Although effective, the rapid progression of the disease restricts the usefulness of anti-anthrax serum. It can be administered for a maximum of 5 days, but due to its high cost, it is not economically feasible for routine application.

Control And Prevention of Anthrax Disease in Livestock

Ensuring proper hygiene is the most crucial factor in controlling and preventing the spread of Anthrax disease in livestock. To achieve this, it is necessary to enforce stringent regulations that require immediate notification, isolation of affected animals, and proper disposal of carcasses.

Disinfection methods such as complete burning of the carcass or deep burial in quick lime to a depth of 2.5 meters should be used.

In addition, quarantine measures must be put in place for at least six months in known infected areas to prevent the spread of the disease to other places.

After disinfection with quaternary ammonium compounds, vaccination of livestock should be carried out using attenuated or virulent strains of Bacillus anthracis. It is recommended to perform annual vaccination for three consecutive years after an outbreak, and immunity typically lasts for one year.

It is essential to note that ropes used during the burying process should be burnt, and personnel must protect themselves from direct contact with carcasses. This can be achieved by wearing heavy rubber gloves, boots, and masks to prevent inhalation of spores. It is also crucial to disinfect all equipment used during the process.

Conclusion

Anthrax, also known as splenic fever, is a highly contagious disease that poses a significant threat to livestock globally. It is caused by the spore-forming bacterium Bacillus anthracis and affects a wide range of animals, with cattle, sheep, goats, pigs, horses, and humans being particularly vulnerable. The disease is characterized by a sudden onset of fever, lethargy, respiratory or cardiac distress, seizures, and eventual death. The hallmark symptom is the extensive enlargement of the spleen (splenomegaly).

Diagnosing anthrax can be challenging, but a postmortem examination is crucial. The absence of blood clotting, lack of rigor mortis, and presence of splenomegaly are important findings. To prevent the spread of anthrax, strict hygiene measures should be implemented, including immediate notification, isolation of affected animals, proper disposal of carcasses, and thorough disinfection of equipment and contaminated areas.

Treatment involves quarantining affected herds, vaccinating healthy livestock, and administering antibiotics to animals showing clinical signs. While antibiotics can be effective, the rapid progression of the disease limits their usefulness. Anti-anthrax serum can be administered but is costly and not economically feasible for routine application.

Preventing anthrax requires a multi-faceted approach, including proper hygiene practices, strict regulations, immediate notification, isolation of affected animals, and vaccination. Disinfection methods such as burning carcasses or deep burial in quick lime should be employed, and quarantine measures should be implemented in known infected areas.

By implementing these control and prevention measures, along with regular vaccination and strict adherence to hygiene protocols, the devastating impact of anthrax can be mitigated, protecting the health and well-being of livestock and minimizing economic losses in the agricultural industry.