Sheza Farooq1, Sanmeet Kour2
1 PhD Scholar, Department of Animal Biotechnology, College of Animal Biotechnology,
2 PhD Scholar, Department of Veterinary Microbiology, College of Animal Biotechnology,
Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, Punjab
Introduction
Hemorrhagic septicemia is a bacterial disease that mainly affects cattle and water buffalo, and is an important cause of livestock mortality. In endemic areas, young animals are primarily affected, and outbreaks are more common during rainy weather, when the organism is easily spread. Within hours to a few days, the clinical signs usually progress from fever and depression to death. Few animals can be treated in time due to the disease’s short duration, and recovery is rare. Disease has the greatest impact on small holder farmers, who have poor husbandry and prevention practices and frequently use free-range management.
Etiology
Hemorrhagic septicemia is an OIE listed disease caused by certain members of Pasteurella multocida subsp. multocida, a Gram-negative coccobacillus in the family Pasteurellaceae. Classically, hemorrhagic septicemia was considered to be caused by just two serotypes of P. multocida ssp. multocida, which are called B:2 and E:2 in the Carter-Heddleston serotyping system, or 6:B and 6:E, respectively, in the alternative Namioka-Carter system. Other serotypes have been isolated from animals with a syndrome clinically indistinguishable from hemorrhagic septicemia (for example, types A:1 and A:3 in cattle and water buffalo in India).
Zoonotic potential
Human infections with P. multocida serotypes B:2 or E:2 have not been reported, and human illnesses have not been linked to animal outbreaks of hemorrhagic septicemia. In humans, however, P. multocida is an opportunistic pathogen, so caution should be exercised to avoid unnecessary exposure. While this organism is most commonly associated with soft tissue infections, it can also cause osteomyelitis, endocarditis, meningitis, respiratory infections, and septicemia, especially in people who are immunocompromised or have other underlying diseases.
Transmission and Pathogenesis
Hemorrhagic septicemia is spread through ingestion or inhalation, either directly or through fomites like contaminated feed and water. The causative organisms are thought to spread primarily through respiratory secretions, but they have also been discovered in other secretions and excretions, such as faeces and urine. Some infected animals become carriers, retaining P. multocida ssp. multocida in lymphatic tissues associated with the upper respiratory tract (e.g., tonsils) and shedding it in nasal secretions on a regular basis. The tonsil and adjacent nasopharyngeal tissues are infected first. Bacteremia causes bacteria to spread and grow rapidly in various locations, tissue injury, a host cytokine response, and the release of lipopolysaccharides, all of which result in a rapidly progressing endotoxemia. Clinical signs may appear 13 days after infection, and death may occur within 824 hours of the onset of clinical signs.
Clinical Findings and Lesions
Fever, hypersalivation, nasal discharge, and laboured respiration are common clinical signs in peracute cases of hemorrhagic septicemia that result in death within 824 hours; however, due to the short duration of disease, these clinical signs may be easily overlooked. Acute disease is defined by a fever of 104°-106°F (40°-41.1°C), apathy or restlessness, reluctance to move, hypersalivation, lacrimation, and nasal discharge that starts out serous and progresses to mucopurulent. Swelling of the pharyngeal region that extends to the ventral neck and brisket (and occasionally the forelimbs), progressive respiratory distress, cyanosis, terminal recumbency, and occasionally abdominal pain with diarrhoea are also seen.
The swelling of the subcutis and muscle of the submandibular region, neck, and brisket by clear to blood-tinged edema fluid is a characteristic lesion of hemorrhagic septicemia. The thorax, pericardium, and abdominal cavity may also contain serous to serofibrinous fluid. In the respiratory, GI, and urinary systems, there is usually widespread congestion with petechiae and ecchymoses in tissues and on serosal surfaces. The pharyngeal and cervical lymph nodes are frequently affected by haemorrhages. In some cases, pulmonary congestion and edema, as well as interstitial pneumonia and gastroenteritis, may occur.
Treatment
Antibiotics are only effective if taken as soon as clinical symptoms appear. During outbreaks, it’s common practise to keep an eye on animals for signs of fever and treat them as soon as possible if they get sick. oxytetracycline, trimethoprim/sulfamethoxazole, a penicillin/streptomycin combination, or sulphaquinoxaline are some of the drugs used to treat hemorrhagic septicemia. In some endemic areas, antibiotic resistance has been observed.
Prevention and control
In countries where hemorrhagic septicemia is not a problem, outbreaks are usually eradicated by stamping them out. Quarantines, movement controls, contact tracing, euthanasia of infected and exposed animals, and cleaning and disinfection of the premises are all part of this process.
Vaccination is the most effective way to prevent this disease in endemic areas. Vaccines for cattle, small ruminants, and pigs may be available. Although annual livestock vaccination is generally recommended, in areas where vaccination coverage is low, ring vaccination is frequently used as part of an outbreak response. Inadequate vaccine coverage is a common cause of HS control failure, owing to a variety of management systems that make annual vaccination difficult. In many cases, vaccination is only done in the event of an outbreak, and it is done with a bacterin (broth or gel) vaccine for rapid coverage in the affected area, followed by ring vaccination with an oil-adjuvant vaccine. The World Health Organization (WHO) has recommended that disease-free zones be established (absence of disease for three years) so that vaccination efforts can be concentrated in areas where infection is common. Intranasal live-attenuated vaccines have also been suggested as a way to boost vaccine coverage by allowing animals in contact with vaccinated animals to self-vaccinate.
Other preventive measures include removing persistent carriers from an infected herd and managing animals to keep them in good health, which is thought to reduce carrier shedding and the risk of asymptomatic carriers developing clinical signs. It is also expected that not crowding animals will reduce transmission and stress levels.
Key Points
- HS is a major disease of cattle and buffaloes characterised by an acute, highly fatal septicaemia with high morbidity and mortality
- In many Asian countries HS disease outbreaks mostly occur during the climatic conditions typical of monsoon (high humidity and high temperatures); however, with climate change, incidences of disease may occur any month of the year
- Vaccination should be routinely practiced in endemic areas. Avoiding crowding, especially during wet conditions, will also reduce the incidence of disease.