Camel ( Camelus dromedarius ) Mastitis in Borena Lowland Pastoral Area , Southwestern Ethiopia

The dromedary camel is a multipurpose animal adapted to the harsh environments of semiarid and arid zones, essentially kept for milk and meat production and transportation. It is also a financial reserve (asset) and security (drought-prone risk management) for pastoralists and plays an important role in social prestige and wealth (8, 19). Because of the increasing desertification and recurrence of drought and famine in subSaharan Africa, particularly in East Africa, the camel plays a very significant role as a source of milk, meat and draft power. In Ethiopia camels are kept in the arid and semiarid lowlands of Borena, Ogaden and Afar regions, which cover 50% of the pastoralist areas in the country. The major ethnic groups owning camels in Ethiopia are the Somali, Borena and Afar (21).


■ INTRODUCTION
The dromedary camel is a multipurpose animal adapted to the harsh environments of semiarid and arid zones, essentially kept for milk and meat production and transportation.It is also a financial reserve (asset) and security (drought-prone risk management) for pastoralists and plays an important role in social prestige and wealth (8,19).Because of the increasing desertification and recurrence of drought and famine in sub-Saharan Africa, particularly in East Africa, the camel plays a very significant role as a source of milk, meat and draft power.In Ethiopia camels are kept in the arid and semiarid lowlands of Borena, Ogaden and Afar regions, which cover 50% of the pastoralist areas in the country.The major ethnic groups owning camels in Ethiopia are the Somali, Borena and Afar (21).
Milk of camel is one of the main components of the diet of the nomads in Ethiopia and is consumed in its raw or naturally processed (soured) form (21). Very little work has been done on mastitis in the camel as the disease was thought to be uncommon in this species (1).However, during the past years mastitis in the camel has been reported from a number of camel-rearing countries of the world (1,2,3,7,10,17).The present study was undertaken to find out the occurrence and bacterial causes of camel mastitis in the camel in Borena, Southwestern Ethiopia (Figure 1).The performance of the California mastitis test (CMT) as a screening test for the detection of mastitis in the camel was evaluated.The relationship between udder infection and somatic cell counts (SCC) was also determined.

Clinical examination of udder and milk
Udder abnormalities such as swelling, presence of lesions or anatomical malformations were recorded.The size of the rear and forequarters, indurations and fibrosis were examined by deep digital palpation.Tick infestations and use of antisuckling devices were also noted.The milk was examined for its consistency, color and other visible abnormalities.Clinical mastitis was recognized by abnormal milk, signs of udder infection and detection of mastitis pathogens by bacteriological culture, whereas subclinical mastitis was recognized by apparently normal milk and an increase in leukocyte counts as evidenced by CMT and a positive culture result.

Milk sample collection
Before milk sampling, the teats were disinfected with cotton moistened with 70% alcohol.After discarding the first few squirts of milk about 20 ml were collected in sterile universal bottles and kept in an icebox, and transported immediately to the laboratory for analysis.Out of 828 quarters examined, 25 (12.1%)teats were blind.Therefore, a total of 803 quarter-milk samples were collected and used for analysis.

California mastitis test
CMT was used according to the procedure described by Schalm et al. (18).CMT score 0 was taken as negative, while CMT scores trace, 1+, 2+ and 3+ were considered positive, thus forming five categorical classes.All milk samples irrespective of CMT results were bacteriologically examined.

Somatic cell counts
SCC were carried out to establish the relationship between the udder infection and the number of cells in camel milk.The direct microscopic somatic cell count (DMSCC) method as described by Packard et al. was used (12).

Isolation and identification of bacteria
Bacteriological examinations were carried out following standard methods (9,14,20).Briefly, a loopful of each milk sample was streaked on 7% sheep blood agar (Merck).MacConkey agar (Merck) plates were also used in parallel to detect Enterococcus species and any Gram-negative bacteria.Inoculated plates were incubated aerobically at 37°C for 24-48 h.Presumptive identification of bacterial isolates was made based on colony morphologic features, Gram-stain reaction, hemolytic characteristics and a catalase test.Staphylococci and Micrococci were identified based on their growth characteristics on mannitol salt agar, coagulase production, catalase and oxidase tests.Isolates identified tentatively as Streptococci were evaluated according to CAMP reaction, growth characteristics on Edward's medium (Oxoid), hydrolysis of esculin and sodium hippurate, catalase production, and sugar fermentation tests.Gram-negative isolates were subcultured on MacConkey agar and further tested using triple sugar iron (TSI) agar (Merck), the IMViC test (indole, methyl red, Voges-Proskauer and citrate utilization tests), urea, lysine and ornithine decarboxylase and oxidase reactions.

■ RESULTS
The majority of camel udders examined were infested with ticks (Amblyomma, Hyalomma and Rhipicephalus species).The teat/udder skin lesions were superficial and old.Twenty-five (12.1%) of the 207 dromedary udders examined had atrophied and blind teats.From a total of 207 lactating camels examined, 4 (1.9%) were clinical cases of mastitis.Clinically affected udders were swollen, hard and painful upon palpation.Camel owners in Borena use antisuckling devices to prevent calves from suckling.For this purpose, they use bark of a tree as a string to tie up pairs of teats together.This is done during daytime when young camels older than one year are herded together with their dams.Table I shows CMT and SCC values and the types of bacteria isolated from clinical cases of mastitis.
Out of 803 quarter-milk samples tested with CMT, 231 (28.8%) were positive.Out of these 231 CMT positive samples, 171 (74%) yielded pathogenic bacteria on culturing.Some of these samples contained bacteria, which gave mixed isolations.A significant agreement percentage was observed between CMT scores and bacteriological findings (Table II).Of the CMT positive milk samples, 26% (60/231) yielded no bacterial growth.
A statistically significant association (P < 0.001) was observed between CMT (when categorizing CMT positive T and all + against negative 0) and cultures (MAP, MIP aggregated into positive cultures) using a chi square test (Table II).
The somatic cell counts of 803 milk samples ranged from 3 x 10 5 to 1.5 x 10 7 leukocytes/ml milk.The overall leukocyte count for NI (non-infected), MIP and MAP bacterial groups indicated that there was a decreasing trend in the range of SCC, respectively.Because of the skewed distribution of SCC among quarter-milk samples examined, SCC was log transformed.It was observed that quarters infected with MAP had higher mean values of SCC than MIP groups and non-infected quarters (Table III).The somatic cell counts for MAP were significantly higher (p < 0.01) than those for MIP and NI.Table IV shows the means of SCC (log scale) with respect to categories of CMT scores.Trend of means given categories of CMT is presented in Figure 2.
Gram-positive cocci were dominant among the total of 818 bacteria isolated from camel milk samples (Table V).

■ DISCUSSION
The udder/teat skin lesions observed in lactating camels could be attributed to the tick burden (Amblyomma, Hyalomma and Rhipicephalus species) infesting the udders and scratches caused by thorny plants of the desert.The use of antisuckling devices in Borena camels is practiced only during daytime when young calves older than one year are herded together with their dams.The use of these devices together with heavy tick infestation could predispose the udders to bacterial infections, which persist as chronic infections.This could result in induration and atrophy of injured quarters (11).Other non-traumatic devices such as the ones used in Mauritania, a protecting harness made of rope named "Shmell" (4), could serve alternatively to reduce injury incidence.
In addition to camels, nomads in Borena keep other animals such as cattle and goats, which could be sources of mastitis pathogens.Other species of animals, which are kept together with camels, could serve as sources of udder infection (11).
The strong positive correlation of CMT with the bacteriological findings indicates that camel milk, like that of cows (18), goats and sheep (5), has phagocytic cells that constitute one of the essential defenses against microbial infections.Milk samples infected with MAP had higher CMT scores.CMT can be used as a screening test to detect subclinically infected udders of camels (3).
The results of the somatic cell counts of the milk samples (between 3 x 10 5 and 1.5 x 10 7 cells/ml) is in agreement with that of Kospakove (1976), cited by Abdurahman et al. (1), who reported a mean of 1.3 x 10 6 cells/milk sample in Bactrian camels.The range of SCC was very small for the MAP group as compared to the MIP and NI groups.Udders infected with MAP had higher values with CMT, SCC and adenosine triphosphate (ATP) than samples from MIP and NI quarters with somatic cell counts of 7.4 x 10 5 -1.2 x 10 7 cells/ml (1).An increase in the number of somatic cells in camel milk with infected quarters has also been reported by Mostafa et al. (10).The possibility that NI quarters have a high SCC can also be supported by the fact that most of the examined camels had lesions on the teats/udder skin because of the string used to tie the teats to prevent suckling or because of ticks.
The rate of milk samples reacting positively with CMT but yielding no bacterial growth was lower (28.2%)than that of Abdurahman et al. (1).They reported that 43% of CMT-positive quarter-milk samples of camels did not show any bacterial growth on appropriate media.This may be because the samples were taken during the convalescent phase of the infection but with a high leukocyte count giving a CMT-positive result.Escherichia coli and other coliforms tend to be of very short duration as they are rapidly destroyed by inflammatory reactions.It has also been reported that 57% of coliform infections usually last less than 10 days and milk samples can be culture negative in 20% of clinical cases of mastitis (14,20).Milk samples from cows with clinical mastitis or from cows whose milk has high somatic cell counts often yield no organism on culture (5).In other cases, the infection may have been eliminated, but an elevated SCC persists still infiltrating the udder tissues.
An increasing trend of mean of SCC and log scale of mean of SCC for CMT scores was observed even though this lacks equal distribution of the frequency of the SCC between the different CMT scores.An increase in milk cell counts also reflects positive CMT results.In the present study, both SCC and CMT results showed they were valuable indicators of udder infections in the camel.An increase in the mean values of both CMT and SCC was observed for the MAP bacterial group as compared to the MIP and NI groups.

Table V
Mastitis pathogens isolated from camels with clinical and subclinical mastitis responsible for subclinical mastitis, but some agents, like Streptococcus agalactiae, were found in both clinical and subclinical mastitis as already described by Younan et al. (22).They reported that Strept.agalactiae and Staph.aureus were found in 12.1 and 10.6% of camel milk samples examined in Kenya, respectively, whereas in the present study 3 and 21% were found, respectively.The increased number of isolates of Strep.agalactiae and other major mastitis pathogens could be attributed to the lack of supply and infrequent use of antimicrobials, and the inaccessibility of the camel owners to veterinary services as compared to dairy cow owners in urban and periurban areas.

■ CONCLUSION
Results of the present study showed that mastitis was prevalent in dromedary camels of the Borena zone of Southwestern Ethiopia, and Gram-positive cocci were the dominant mastitis pathogens isolated.The positive correlation of CMT with the presence of mastitis pathogens in camel milk showed that CMT is a useful screening test in the detection of mastitis in camels and may serve to segregate udders infected with major pathogens in a subclinical form.Increase in the somatic cell counts of infected quarters indicated that camels reacted to inflammation induced by agents of mammary tissue by raising the number of somatic cells in the milk.However, further investigation is needed to determine the infection threshold of SCC in camel milk.

Table II
Relation between the California mastitis test (CMT) scores and bacteriological results of camel milk samplesCMT score (positive = trace, 1+, 2+, 3+, versus negative 0) and culture results (positive versus negative) with significant association, Chi square P < 0.001