Diseases impacting lion populations: Potential Threats

By ALERT
Last updated 7 Mar 2012

 

Potential disease threats not yet identified in free ranging lion populations


Feline Leukaemia Virus (FeLV)

Feline leukaemia virus (FeLVs) can be classified into three subgroups: A, B and C and are pathogenic retroviruses that induce proliferative, degenerative and immunosuppressive disorders [1-2].   The disease can be transmitted via saliva (ie, grooming each other), through nasal secretions or across the placenta from a queen to its developing foetuses. [3]

This disease is a cancer of the blood cells known as lymphocytes.  The main systems to be affected are lymphatic, immune and nervous however all other body systems can be affected due to secondary infections.   Initial symptoms include – Lymphadenomeagly (enlarged lymph nodes), rhinitis, persistent diarrhoea, gingivitis and progressive ataxia (the ‘’wobbles’’/collapsing) [2]

In cases of infected animals, several antiviral agents have been proposed. Unfortunately, administration of a ‘reverse inhibitor AZT’ does not appear to clear viremia in most felines. The prognosis for infected animals is guarded and the majority die within in 2 – 3 years. [3]

Non symptomatic individuals can harbour a latent infection in a dormant state within bone marrow and may be reactivated if the immune response is compromised or removed.  The latent viral infection is eliminated over time however evidence suggests that virus shedding may occur from a queen to her young through milk [4].  Whether latently infected individuals can shed the virus by other means is undetermined.

To date no evidence of the virus infecting wild lions has been discovered although clinical signs may be missed in populations not under close observation, so lack of pathogenicity should not be assumed.  Seronegative samples have so far been collected from populations including Queen Elizabeth National Park, Uganda [5], Serengeti National Park, Ngorongoro Crater and the Lake Manyara area in Tanzania [6-7], various locations in Botswana [8] and Zakouma National Park, Chad [9]


Feline Monocytotropic Ehrlichiosis

Ehrlichia is a tick-borne obligately intracellular bacterium of the family Rickettsiaceae that infect white blood cells causing monocytotropic ehrlichiosis [1]. 

Common clinical signs include anorexia, lethargy, weight loss, vomiting or diarrhoea, pale mucous membranes, joint pain, lymphandenomeagly and dyspnoea (shortness of breath) (2)  Non-regenerative anaemia or thrombocytopenia (low platelet count) and low white blood cell counts have been observed in laboratory blood tests.

Whilst seropositive results for the antigens in African lions have not been identified results from some captive wild felids and domestic cats have been [4]. 

Read the next chapter of this article here


References for Feline Leukaemia Virus

[1]  Shalev Z, Duffy SP, Adema KW, Prasad R, Hussain N, Willett BJ, Tailor CS (2009)  Identification of a feline leukaemia virus variant that can use THTR1, FLVCR1, and FLVCR2 for infection.  Journal of Virology 83 (13) 6706-6716 (pdf)

[2]  Fujino Y, Ohno K, Tsujimoto H (2008) Molecular pathogenesis of feline leukaemia virus-induced malignancies:  Insertional mutagenesis.  Veterinary Immunology and Immunopathology 123: 138-143 (pdf)

[3]  Nelson RW, Couto CG (2009) Small Animal Internal Medicine, 4th Edition, Mosby Title (book – purchase required)

[4]  Jarrett O (1985) Feline leukaemia virus .  In Practice 7: 125-126 (pdf)

[5]  Driciru M, Siefert L, Prager KC, Dubovi E, Sande R, Princee F, Friday T, Munson L (2006). A serosurvey of viral infections in lions (Panthera leo), from Queen Elizabeth National Park, Uganda. Journal of Wildlife Diseases, 42(3), 667-671. (pdf)

[6]  Hofmann-Lehmann R, Fehr D, Grob M, Elgizoli M, Packer C, Martenson JS, O’Brien SJ, Lutz H (1996) Prevalence of antibodies to feline parvovirus, calicivirus, herpesvirus, coronavirus, and immunodeficiency virus and of feline leukemia virus antigen and the interrelationship of these viral infections in free-ranging lions in east Africa, Clinical and Diagnostic Laboratory Immunology 3: 554–562. (pdf)

[7]  Packer C, Altizer S, Appel M, BrownE, martenson J, O’Brien SJ, Roelke-Parker M, Hofmann-Lehmann R, Lutz H (1999) Viruses of the Serengeti: patterns of infection and mortality in African lions. Journal of Animal Ecology 68: 1161-1178  (pdf)

[8]  Osofsky SA, Hirsch KJ, Zuckerman EE, Hardy jr. WD (1996) Feline lentivirus and feline oncovirus status of free-ranging lions (Panthera leo) Leopards (Panthera pardus), and cheetahs (Acinonyx jubatus) in Botswana: A regional perspective.  Journal of Zoo and Wildlife Medicine 27 (4) 453-467 (pdf – purchase required)

[9]  Vanherle N (2005) Interim report of the Zakouma Lion Study.  IUCN/SSC Cat Specialist Group. (pdf)

Further reading:

Emerging Viruses in the Felidae: Shifting Paradigms (pdf)
O’Brien SJ, Troyer JL, Brown MA, Johnson WE, Antunes A, Roelke ME, Pecon-Slattery J (2012). Viruses 4: 236-257 


References for Feline Monocytotropic Ehrlichiosis

[1]  Thomas S, Popov VL, Walker DH (2010)  Exit Mechanisms of the Intracellular Bacterium Ehrlichia. PLoS ONE 5(12): e15775  (pdf)

[2]  Lappin MR {2003)  Update on Two Feline Parasites:  Ehrlichia and Hemobartonella.  Report of the Winn Feline Foundation 25th Annual Feline Symposium (pdf)

[3]  Shaw SE, Day MJ (2005) Arthropod–borne Infectious Diseases of the Dog and Cat Manson Publishing Ltd pp 120 – 133 (book – purchase required)

[4]  André MR, Adania CH, Machado RZ, Allegretti SM, Felippe PA, Silva KF, Nakaghi AC (2010) Molecular and serologic detection of Ehrlichia spp. in endangered Brazilian wild captive felids.  Journal of Wildlife Diseases 46 (3): 1017-23 (pdf)