Pasteurellosis
Pasteurellosis or hemorrhagic septicemia in Asian elephants has been report in several countries in Asia, where it is a common disease in water buffalo and other ruminants. In elephants it can cause a severe generalized disease, which is often fatal. The causative pathogens are Pasteurella multocida and Mannheimia (Pasteurella) haemolytica. They are nonmotile, facultative anaerobic and may exhibit bipolar staining with Giemsa or Wright’s stain.
Transmission of the pathogen can be through direct or and indirect contact and possibly through biting insects and wound contamination. It is generally assumed that Pasteurella spp. are secondary pathogens that may strike when the immune system is challenged by a primary disease or stressful condition.
Higher magnification of lung impression smear showed bipolar characteristic Pasteurella sp. (Harish, 2009)
Inapparent infections have not been reported, though vaccination-induced antibodies against P. multocida can be detected using an indirect ELISA (Tankaew, 2017). This indirect ELISA was more sensitive in elephants than the indirect hemagglutination assays (IHA), which is the WHO recommended diagnostic test in farm animals.
The epidemiology of hemorrhagic septicemia is not fully known. However, multiple cases were reported following periods of consecutive droughts from 2010 to 2012 and sudden heavy monsoon rains in India in 2013 (Chandranaik, 2016).
Clinical symptoms
Clinical symptoms may vary, ranging from its presence in foot abscess to an acute fatal disease. The FAO manual for elephant managers describes the following signs, which might be associated with hemorrhagic septicemia:
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There is a high fever. Take the elephant's temperature. (See page 71.) If it is over 37.8° C or 100° F, that is a sign of danger.
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The breath exhaled from the mouth and trunk is very hot.
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There is a bright red at the eyes, mouth, the end of the trunk, and other soft tissue.
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Swelling (edema) is found in body parts such as the throat, the shoulders, the base of the tail, the anal flap, on the belly under the legs.
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The elephant is listless, the trunk rests on the ground, and the ears do not flap.
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The elephant does not eat.
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The elephant frequently opens its mouth to "yawn".
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The body trembles and has spasms because breathing is difficult.
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The urine is cloudy and richly coloured.
In fatal cases pneumonia, hemorrhagic tracheitis, haemorrhages on the heart, and/or lesions of acute septicemia in all other vital organs have been described (Harish, 2009; Srivastav, 2017).
Pasteurellosis presents in varies forms, so many other diseases must be considered in a differential diagnosis, including anthrax, trauma, foreign-body reactions, staphylococcosis, salmonellosis, and pneumonia caused by various agents.
Diagnosis
Isolation and identification of Pasteurella spp. or Mannheimia haemolyticum combined with a disease presence leads to the diagnosis of hemorrhagic septicemia. If diagnosed, one should always consider that there might be involvement of another primary disease process! Confirmation of the diagnosis by PCR may lead to the source of the infection if other elephants of other animal species are involved.
Treatment
Immediate treatment is required when hemorrhagic septicemia is suspected. Pasteurella sp. are usually susceptible to amoxycillin, trimethoprim+sulfa an fluoroquinolones (like enrofloxacin). Antimicrobial therapy can be initiated using one of the above mentioned drugs, however samples should be taken for culture and as soon as the sensitivity of the pathogens have been determined, the therapy should be adjusted according to the antibiogram results.
Supportive therapy consists of administration of fluids (rectally and/or intravenously). NSAIDs should be given if the general condition or pain reactions indicate their use.
For dosages go to: https://elephantcare.org/resources/formulary/drug-index/.
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Make sure that no mahouts or other people who have been in contact with the ill elephant have any contact with the healthy elephants.
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The healthy elephants should be taken to a place where they have no contact with dung, urine, or uneaten food of the infected elephant.
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Feed the elephant with items of high nutritional value, such as bananas, unhusked rice, sugarcane, and high quality browse.
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When an elephant dies of hemorrhagic septicemia, the carcass must be buried or burned. The carcass should not be butchered for meat or to remove the tusks to sell because this can spread the disease to other elephants and to other animals.
The FAO has elaborated an action plan for additional measures in case of hemorrhagic septicemia in elephants (see Elephant Care Manual for Mahouts and Camp Managers):
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Immediately separate the infected elephant and keep it as far away as possible from other animals.
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Take the infected elephant to a clean, quiet and shady spot that is easily cleaned and where run-off water and waste, such as dung and uneaten food, do not contaminate other areas.
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Most importantly, ensure that the water source for sick animals and healthy animals is separate. If there is only one source of drinking water, it is likely contaminated. If so, try to get the healthy animals to a new source of water. You might even have to truck water in, but you must ensure your animals are drinking pure water free of infection.
Prevention
In several Asian range countries elephants are vaccinated with the vaccines available for cattle, like an inactivated aluminium-precipitated vaccine used in (non-pregnant) elephants over 6 months that used to work in the timber industry in Myanmar (5ml, subcutaneous, twice a year).(pers. Comm. Khyne U Mar, 2023). Contact with susceptible farm animals, especially water-buffaloes and cattle should be avoided.
Outbreak of Pasteurellosis in free ranging African elephants
During a period of 4 months in 2020 a total of 35 African elephants were found dead in north-western Zimbabwe. The estimated age of the dead elephants ranged from 18 months–30 years. Elephants of both sexes were found dead (16 males, 9 females).
The carcasses were in average body condition with hepatomegaly and splenomegaly as the most prominent gross pathological findings, with variable hemorrhages across the epicardium, liver, lungs, intestinal serosae, hepatic and splenic lymph nodes, and in one case, the diaphragm. Histopathological lesions in elephants were similar and consisted of acute multifocal heterophilic and necrotizing inflammation in liver, spleen, and lymph node, with presence of intralesional Gram-negative bacterial colonies of coccobacillary morphology. Specifically, one elephant displayed necrotizing lesions in spleen and liver, with the additional presence of fibrinocellular and bacterial emboli in the pulmonary vasculature. Presence of Gram-negative bacterial colonies without associated morphological changes was observed in veins and capillaries, prominently in the encephalon. Acute multifocal heterophilic and necrotizing lymphadenitis, hepatitis and splenitis with intralesional Gram-negative coccobacilli was observed in one. Most blood smears (n = 13/15) stained with Giemsa contained small to moderate numbers of bacteria with a bipolar, short-rod, or coccobacilli morphology (0.5–2 µm), and intracellular bacteria were observed.
Of 15 sampled elephants, six showed molecular evidence of septicemic infection by Bisgaard taxon 45. There was no evidence of toxins, including those from cyanobacteria, or for any viral infection. The failure to identify Bisgaard taxon 45 in samples from all 15 elephants is likely due sample quality and delays in testing.
The authors propose that stress from a combination of heat, drought, and population density were likely contributing factors in this outbreak. Food and water resources normally wane as temperatures rise during the dry season, and elephants must travel increasing distances between water points and foraging areas.
The source of infection and route of transmission remain unknown in this outbreak.
For more details about this mass die-off, click here.
References
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Chandranaik BM., Shivashankar BP., Giridhar P., and Nagaraju DN. 2016. Molecular characterisation and serotyping of Pasteurella multocida isolates from Asiatic elephants (Elephas maximus). Eur J Wildl Res (2016) 62:681–685
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FAO: Elephant Care Manual for Mahouts and Camp Managers.
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Tankaew P., Singh-La T., Titaram C., Punyapornwittaya V., Vongchan P., Sawada T., Sthitmatee N. 2017. Evaluation of an In-house indirect ELISA for detection of antibody against haemorrhagic septicemia in Asian elephants Journal of Microbiological Methods. Vol.134, pp30-34.