Cheetah (Acinonyx jubatus)- Data, Pictures & Videos

[Acinonyx sp.]

CHAPTER 8: THE INCIDENCE OF DENTAL ABNORMALITIES IN WILD CAUGHT NAMIBIAN CHEETAHS 

ABSTRACT 
Two hundred and eight cheetahs that were opportunistically live-trapped on Namibian farmlands were examined for signs of dental abnormalities. Three abnormalities were recorded: erosion of the upper palate, possibly a predisposition to focal palatine erosion, where the first lower molar penetrates the palatine mucosa; crowding of the lower incisors; and the absence of one or both upper premolars. Just over 40% of the cheetahs examined showed deep palatine erosion, and 15.3% of these had perforated upper palates. In addition, 31.7% of the cheetahs examined had crowded lower incisors and 20.9% had one or both upper premolars missing. The incidence of focal palatine erosion is of particular interest as it has only been recorded in captive cheetahs, where it was attributed to a ‘soft’ captive diet, and never before in completely wild individuals. To attempt further understanding of the potential causes of such erosion, the condition was examined in relation to sex, age, region, time in captivity, and the occurrence of other dental abnormalities. No relationship was found between the severity of the condition and time spent in captivity, while juveniles showed more severe erosion than adult cheetahs. Cheetahs missing either one or both upper premolars showed a higher incidence of deep erosion, and the same was true for cheetahs that exhibited crowded lower incisors. The traditional explanation of focal palatine erosion being an artifact of captivity does not explain its occurrence in this sample population of cheetahs, the majority of which were raised entirely in the wild.

8.1 INTRODUCTION
 Focal palatine erosion is a health problem that has been identified in captive cheetahs, in which the first lower molar penetrates the upper palate, medial to the upper first molar (Fitch and Fagan 1982, Phillips et al. 1993). In unaffected cheetahs, there is a slight indentation of the palatine mucosa in this general area, to accommodate the cusp of the tip of the lower first molar. This erosion is a serious problem that has the potential to cause severe health problems and even fatal disease in individuals, especially when penetration of the hard palate occurs. The pathogenesis of FPE occurs where the lower molar’s tip makes regular contact with the palatine mucosa, so the tooth eventually penetrates through the palatine bone itself, causing inflammation. The oral defects observed in affected cheetahs range from sparse cellulitis, the loss of pigmentation and signs of inflammation, to large oral-nasal bony defects extending through the palatine bone into the nasal passage (Fitch and Fagan 1982). Particles of food which lodge in the focal palatine defect result in localised infection and further tissue damage. FPE has been reported in captive cheetahs as early as 10 months of age with a slight, localised cellulitis, although in young cats it may be overlooked as a typical ‘teething’ disorder (Fitch and Fagan 1982).Although this condition has never previously been reported in cheetahs that were born and raised in the wild, the majority of reported cases have occurred in Namibian wild-caught animals living in captivity and captive-born animals from Namibian founders. When first reported, 86% of the cheetahs with FPE came from one shipment from Namibia in 1970 or their descendants (Fitch and Fagan 1982). This oral defect was attributed to the feeding of soft commercial diets lacking bones on developing cheetahs (Phillips et al. 1993), as well as the possibility of specific family lines, renal disease, suppurative rhinitis, and appears to often accompany, but not always, a maloccluded dentition (Fitch and Fagan 1982). During examinations of cheetahs handled by the Cheetah Conservation Fund, the opportunity was taken to investigate any dental abnormalities that were observed in wild cheetahs. In addition to focal palatine erosion, other dental abnormalities observed in our sample population were the crowding of the lower incisors, and the absence of one or both upper premolars. The crowding varies from slight crookedness to a severe condition where the incisors are arranged in two parallel rows. In domestic dogs and cats, such problems usually have a genetic basis, although nutritional status, juvenile viral infections, and metabolic disorders are also possible causes (Colmery and Frost 1986, Frost and Williams 1986). The absence of one or more premolars has been recorded in cheetahs before (Ewer 1973), but the objective in this study was to examine this phenomenon in relation to the other abnormalities recorded, particularly the erosion of the upper palate. Before investigation into the impact, prevalence, and etiology of such dental abnormalities can be undertaken, the anomalies must be properly defined, characterized, and described in literature. The reporting of these conditions, particularly focal palatine erosion, in entirely wild cheetahs is important for other researchers, to encourage further investigation, and to aid in the determination of the ultimate causes of focal palatine erosion and its impact on wild cheetahs. 

8.2 METHODS 
Cheetahs were examined after being opportunistically live-trapped on Namibian farms, as described in Chapter 3, and had been held in captive situations for varying lengths of time before the Cheetah Conservation Fund was invited to examine them. The region and date of capture was determined whenever possible, and cheetahs that had been held in captivity for 30 days or more by the time of examination were considered to be ‘captive’ animals. Age classification followed the protocol described in section 3.1, but in order to enable comparisons to be made, we condensed our age classes into the scheme et out in Phillips et al. in (1993), which used four classes for analyses: (1) Juvenile cheetahs (24 months old or less at the time of exam) that had been captured before adult tooth eruption (before seven months old); (2) Juvenile cheetahs captured at seven months old or later; (3) Adult cheetahs (over 24 months old) that had been captured when juvenile (seven to 24 months old) and; (4) Adult cheetahs that were captured over 24 months old. Each cheetah was examined for signs focal palatine erosion (FPE) and evidence of other dental abnormalities. A score of 1 was assigned in cases where there was very little or no sign of erosion, a score of 2 indicated a medium erosion, and in cases where erosion had caused a deep depression the condition was scored as a 3. Some of the cases scored as 3 also showed actual focal palatine erosion, signified by perforation of the mucosa, sometimes accompanied by bleeding, inflammation, and signs of foreign matter, and this was recorded as well. Callipers were used to measure particular teeth and intraoral photographs were taken. The overall score for analysis was developed as follows: 1 = a score of 1 on both sides of the palate 2 = a score of 1 on one side and 2 on the other 3 = a score of 2 on both sides 4 = a score of 2 on one side and 3 on the other 5 = a score of 3 on both sides. None of the cheetahs examined had scores that did not fit this scheme, e.g. a score of 1 on one side and 3 on the other. The degree of erosion was considered to be severe if ne or both sides of the palate were scored with a 3. The number of upper premolars was examined for each cheetah, with resulting scores of 0 (no premolar on either side), 1 (one premolar present on one side) and 2 (both premolars present), while the lower incisors were also examined to see whether there was any crowding. Cheetahs were also weighed and their physical condition assessed, looking at factors such as coat condition, musculature, ectoparasite load etc. This excluded injuries that were likely to have been sustained while in the capture cage, to give a better indication of condition in the wild. Statistical analyses were performed using SPSS version 10.0 software (SPSS Inc. Chicago, USA). Means significance testing was carried out using the parametric independent samples t-test, preceded by Levene’s test for equality of variances, and general linear model univariate analyses. Departures from expected ratios were analyzed using Pearson’s chi-squared test, while the non-parametric Spearman’s rank correlation coefficient was used to determine the significance of relationships between variables measured on ordinal scales. All tests are two-tailed unless otherwise stated. 

8.3 RESULTS 
Two hundred and eight cheetahs were examined for dental abnormalities between June 1992 and November 1999, and the breakdown of this sample population is shown in Table 8.1. Almost two-thirds (62.5%) of the cheetahs examined were male, while a similar proportion (67.3%) were wild, i.e. had been held captive for under 30 days. 

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Precise dates of capture were available for 94.2% (n = 196) of the examined cheetahs and these animals could therefore be assigned to the four age classes described above. Overall, 87 juvenile cheetahs were examined, 12.6% of which (n = 11) were captured before seven months old (Table 8.1). Although the single most common score assigned was 1, the incidence of deep erosion was relatively high, with 40.9% of the sample population classified as having a deep depression on at least one side of the palate (Table 8.2). Thirteen (15.3%) of these cheetahs (6.3% of the sample population) had perforations in the upper palate as a result of this severe focal palatine erosion.

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The frequency of deep erosion amongst cheetahs that had been held captive for 30 days or more was 42.6% (n = 29), while the condition was slightly milder in wild 
cheetahs, with 40.0% (n = 56) showing severe erosion. There were no significant differences between wild and captive cheetahs, however, regarding overall score (F 2 = 3.573, d.f. = 4, P = 0.467), the incidence of severe erosion (F 2 = 0.133, d.f. = 1, P = 0.716), or the development of palatine perforation (F 2 = 1.142, d.f. = 1, P = 0.285). When just captive cheetahs were examined, there was a slight positive correlation between the score assigned and the length of time spent in captivity, although it was not statistically significant (rs = 0.203, n = 57, P = 0.129). Figure 8.1 shows the mean scores by sex for the different age classes. There was no difference between sexes in overall scores (F 2 = 4.980, d.f. = 4, P = 0.289), the frequency of severe erosion (F 2 = 2.017, d.f. = 1, P = 0.156), or perforated FPE (F 2 = 0.005, d.f. = 1, P = 0.941). There was some slight variation, however, in scores between different regions of the country (F = 2.026, d.f. = 8, P = 0.045).

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Age did appear to play a significant role in the severity of erosion: juvenile cheetahs had significantly higher overall scores than the adults (F 2 = 13.645, d.f. = 4, P = 0.009), were subject to significantly more severe erosion (F 2 = 9.930, d.f. = 1, P = 0.002), and were significantly more likely to show perforated erosion (F 2 = 5.971, d.f. = 1, P = 0.015). There was no significant difference in the severity of the erosion seen between those juveniles captured before adult tooth eruption and those captured when older (F 2 = 0.859, d.f. = 1, P = 0.354). Adult cheetahs captured as juveniles had a lower incidence of severe erosion than those captured when adult already, although the difference was not statistically significant (F 2 = 3.725, d.f. = 1, P = 0.054). Data regarding the number of premolars and the frequency of crowded incisors are shown in Table 8.3 for captive and wild cheetahs examined of different ages. 

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The number of premolars that a cheetah had was significantly linked to the severity of erosion – those cheetahs that had either one or both upper premolars missing showed a significantly higher frequency of severe erosion than those with both premolars present (F 2 = 7.251, d.f. = 2, P = 0.027). The frequency of severe erosion was also significantly higher amongst cheetahs that had crowded lower incisors than those that did not (F 2 = 4.537, d.f. = 1, P = 0.033), although there was no significant relationship for perforated FPE (F2 = 0.290, d.f. = 1, P = 0.590). There was a relationship between the incidence of severe erosion in wild cheetahs and poorer physical condition, as shown in Figure 8.2. Wild cheetahs with severe erosion were significantly less likely to be in excellent condition (F 2 = 11.296, d.f. = 1, P < 0.001). While wild cheetahs that had severe erosion were lighter in mass than those without a severe condition, with a mean mass of 33kg compared to 36kg, this difference was not statistically significant (t = 1.203, d.f. = 135, P = 0.231). There was no significant relationship between crowded incisors and either being in excellent physical condition (F 2 = 0.673, d.f. = 1, P = 0.412), or body mass (t = 1.429, d.f. = 135, P = 0.155).

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8.4 DISCUSSION 
Although focal palatine erosion was first formally recorded in the captive cheetah population almost 20 years ago, it was believed not to occur in wild cheetahs captured as adults (Fitch and Fagan 1982, Phillips et al. 1993). During this long-term study conducted on Namibian farmlands, however, we found not only evidence of erosion in wild cheetahs that may lead to focal palatine erosion, but also found that it was not uncommon, with 40% of wild cheetahs showing deep erosion on at least one side of the palate. Even more notably, six percent of the cheetahs examined were suffering from perforated palates (the most severe form of focal palatine erosion), including seven animals that had never been held in captivity. This shows that the preconditions for FPE exist in the free-ranging cheetah population throughout Namibia, with slight variations by region. A common explanation for the development of focal palatine erosion has been that cheetahs brought into a captive situation are fed artificially ‘soft’ diets, which fail to sufficiently wear down the carnassials and hence lead to palate damage (Fitch and Fagan 1982, Phillips et al. 1993). This does not explain, however, the results presented here, which show that cheetahs reared on an entirely natural, wild diet also suffer from the same problem. The effect of diet on tooth wear may indeed be important, and is supported in this study by the evidence that the degree of erosion appears to increase with time spent in captivity, although the trend here was not found to be statistically significant. The fact that the captive cheetahs we examined showed a slightly higher incidence of severe erosion also hints towards some effect of captivity, but we feel that focusing entirely on the issues of diet and captivity as the sole explanation may be misleading. The juvenile cheetahs examined showed a significantly higher degree of erosion than did the adults, regardless of how old they were when they were captured, and were also more likely to suffer from perforated focal palatine erosion. Although wild cheetahs consume primarily muscle and skin (van Valkenburgh 1996), bone consumption at kills has been recorded to varying extents (Brain 1981, Phillips 1993). It seems likely that the gradual wear from gnawing on tough cartilage and bones will eventually blunt the teeth of adult cheetahs and reduce the extent to which the molar can irritate and penetrate the palatine surface. In 1982, Fitch and Fagan suggested that malocclusion of the teeth could be a anomalies similar to those reported here have been observed in the highly inbred populations of captive white tigers (Emily, P., pers. comm.), while other morphological abnormalities have been reported in Florida panthers, which also show very little genetic variability (Johnson et al. 2001, Roelke et al. 1985). The combined allozyme study on Namibian cheetahs and the morphological data suggests a genetic explanation (O'Brien et al. 1983, Wayne et al. 1986). The dental abnormalities as described in this paper may prove to be a genetic condition that predisposes an individual to developing advanced focal palatine erosion. Extensive work has already been done on cheetah genetics (Menotti-Raymond and O'Brien 1993, O'Brien et al. 1985, O'Brien et al. 1987, O'Brien et al. 1983) and protocols exist for both DNA fingerprinting and microsatellite analysis (Gilbert et al. 1991, Menotti-Raymond and O'Brien 1993). Both of these techniques will be used in the near future to examine relatedness of animals with and without these morphological abnormalities. While the occurrence of focal palatine erosion in wild cheetahs is interesting from a scientific standpoint, the most crucial factor is whether it appears to have a detrimental effect on the cheetahs that exhibit it and on the population overall. Phillips et al. (1993) found with captive animals that even those cheetahs that had FPE were in excellent condition, but we found that in our sample there was a relationship between severe FPE and a loss of physical condition. It is not yet known in what way the dental abnormalities described will impact on the cheetah’s ecology, nor what the consequences will be in the long-term. For example, wild cheetahs are known to suffer from kleptoparasitism by larger, more powerful carnivores such as lions and hyaenas (Caro 1994), and if cheetahs with dental abnormalities are slower at processing their kills, they may be at a further disadvantage in the wild by losing more of their kills in this way. It is also unknown what the implications of the physical defects, such as perforated palates as seen in extreme cases of FPE, may be for the overall health of affected wild individuals, although we know that they can lead to serious physical problems in captivity. For instance, one of the captive cheetahs reported with FPE died from severe kidney failure that was associated with oral-nasal osteomyelitis from FPE (Fitch and Fagan 1982), and kidney failure is one of the main causes of death for captive cheetahs (Marker-Kraus 1997, Munson 1993). Overall, the development of dental abnormalities, including focal palatine erosion, is likely to be multifactorial, with genetics, diet, time spent in captivity, age and skull morphology all playing a role. The reporting of these conditions in wild cheetahs is important, as raising awareness amongst researchers will be vital in order to gain more information regarding the prevalence and severity of such abnormalities in different cheetah populations. This information will be crucial for a better understanding of how these conditions, particularly focal palatine erosion, may develop amongst wild cheetahs as well as those in captivity. 

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