Idiopathic hemorrhagic vasculopathy syndrome in seven black rhinoceros

COAGULATION ASSESSMENT: UNDERUTILIZED DIAGNOSTIC TOOLS IN ZOO AND AQUATIC ANIMAL MEDICINE

Veterinarians specializing in nondomestic species are faced with unique challenges regarding research and diagnostic capabilities given the wild and frequently dangerous nature of their patients. Standard diagnostic techniques used in small or large animal practice are not always possible due to anatomical constraints, size, tractability, or the inherent risk of anesthesia in highly valued, rare species. Diagnostic modalities that utilize simple, relatively noninvasive techniques show promise in evaluating nondomestic species and elucidating the pathophysiology behind poorly characterized disease processes in both wild and captive populations. Coagulation profiles, which may include prothrombin time (PT), partial thromboplastin time (PTT), D-dimer concentration, platelet count, and thromboelastography (TEG) are frequently used in domestic species but often overlooked in exotic medicine due to lack of normal reference values and/or availability. Whenever possible, coagulation profiles should be utilized in the evaluation of various disease processes including neoplasia, sepsis, trauma, inflammation, toxin exposure, and envenomation. There are several reports of coagulopathies in both wild and captive species; however, few studies on coagulation profiles have been published on nondomestic species. Clinicians should consider coagulation testing as part of the diagnostic work-up in nondomestic species. A review of available coagulation diagnostic tests is provided here in addition to summarizing the pertinent coagulation disorders currently established in the literature.

Vasculitis secondary to presumptive leptospirosis treated with long-term corticosteroids in a captive lesser kudu (Tragelaphus imberbis australis)

A 2-yr-old female lesser kudu (Tragelaphus imberbis australis) was presented for lethargy. Empirical antibiotic treatment appeared to improve its clinical signs, although no etiology for the symptoms was determined. The kudu again presented with lethargy, diffusely swollen limbs, and subcutaneous ecchymoses of 1 day's duration after completion of the initial therapy. Vasculitis secondary to presumptive leptospirosis infection was diagnosed based on a skin biopsy and decreasing paired serologic titers for Leptospira grippotyphosa. The vasculitis was responsive to intramuscular antibiotic therapy and dexamethasone treatment. This case provides evidence that corticosteroids can be used in ruminants at moderate doses for chronic treatment without clinically relevant detrimental effects.

A review of some of the health issues of captive black rhinoceroses (Diceros bicornis)

In captivity, black rhinoceroses (Diceros bicornis) are beset by many disease syndromes not described in black rhinoceroses in the wild. Hemolytic anemia, hepatopathy, and ulcerative dermatopathy that lead to increased morbidity and mortality characterize these syndromes. It is uncertain whether these are separate disease syndromes with different etiologies or the same disease with different manifestations. This article offers a brief review of some of the health issues of concern for the captive black rhinoceros population and proposes some possible avenues of research for consideration.

Corticosteroid-induced suppression of in vitro lymphocyte proliferation in four captive rhinoceros species

Captive African black rhinoceroses (Diceros bicornis) are unusually susceptible to several diseases not commonly observed in any of the other three rhinoceros species maintained in captivity. The potential role of corticosteroids (either endogenously produced or exogenously administered) in the development of these sometimes fatal diseases has been questioned. In this study, the suppressive effects of two therapeutic corticosteroids (dexamethasone and hydrocortisone) on in vitro lymphocyte proliferation was examined in four rhinoceros species, including the Sumatran rhinoceros (Dicerorhinus sumatrensis, n = 3), Indian rhinoceros (Rhinoceros unicornis, n = 4), African black rhinoceros (n = 10), and African white rhinoceros (Ceratotherium simum, n = 5). Three blood samples collected from each rhinoceros 1 mo to 1 yr apart provided replicates for the study. Both dexamethasone and hydrocortisone suppressed (P < 0.05) lymphocyte proliferation stimulated by B-cell mitogens (pokeweed and lipopolysaccharide) and T-cell mitogens (phytohemagglutinin and concanavalin A). Suppressive effects of the glucocorticoids differed (P < 0.05) depending on the mitogen used to stimulate the lymphocytes. Overall, dexamethasone was a more potent suppressor of cell proliferation when compared with hydrocortisone (P < 0.05). However, black rhinoceros cell proliferation in response to any of the four mitogens was never completely suppressed, even in cultures containing the highest steroid concentration tested (10(-3) M). The effect of the two corticosteroids differed slightly among the rhinoceros species and subspecies tested, but there was no evidence that eastern or southern black rhinoceros lymphocytes were more sensitive to the suppressive effects of corticosteroids than the other rhinoceros species.

Comparative studies of mitogen- and antigen-induced lymphocyte proliferation in four captive rhinoceros species

Cellular immune function in four rhinoceros species was evaluated by way of in vitro lymphocyte proliferation responses to mitogenic and antigenic stimuli to establish normative data on white blood cell activity for each species and to identify species-specific differences that might help explain the predisposition of black rhinoceroses (Diceros bicornis) to disease. A cross section of the U.S. rhinoceros population encompassing all four captive species was sampled, including the Sumatran rhinoceros (Dicerorhinus sumatrensis) (n = 3); Indian rhinoceros (Rhinoceros unicornis) (n = 4); African black rhinoceros (n = 16); and African white rhinoceros (Ceratotherium simum) (n = 10). Of the four species evaluated, African black rhinoceroses exhibited the weakest (P < 0.05) lymphocyte proliferative responses to the mitogens: pokeweed (0.1 microg/ml), phytohemagglutinin (0.3 microg/ml), and concanavalin A (5.0 microg/ml). Total cell density at the end of culture was only 70% of that achieved with lymphocytes isolated from African white rhinoceroses, Indian rhinoceroses, and Sumatran rhinoceroses. However, lymphocyte response to bacterial endotoxin lipopolysaccharide was similar (P > 0.05) across species. Antigenic stimulation produced much weaker responses than mitogenic stimulation. No differences (P > 0.05) were observed among rhinoceros species in response to 1 and 10 microg/ml of Leptospira icterohemorrhagiae or Leptospira gryppotyphosa. Lymphocytes from African white rhinoceroses proliferated weakly in the presence of Aspergillus fumigatus filtrate, whereas lymphocytes from the southern black rhinoceros subspecies appeared slightly suppressed in the presence of increasing doses (0.1, 1, and 10 microg/ml) of Aspergillus filtrate. This comparative data set characterizing lymphocyte proliferation in the rhinoceros reveals several differences in immune cell responses among rhinoceros species and provides some evidence that lymphocytes of captive African black rhinoceroses are less vigorous than those of the other rhinoceros species.

Babesia bicornis sp. nov. and Theileria bicornis sp. nov.: tick-borne parasites associated with mortality in the black rhinoceros (Diceros bicornis)

A novel Babesia species, designated Babesia bicornis sp. nov., was identified in three black rhinoceroses (Diceros bicornis) that died in wildlife areas in Tanzania and South Africa. Screening of black rhinoceroses in South Africa revealed, in addition to B. bicornis, a second parasite, designated Theileria bicornis sp. nov.