ISRAEL JOURNAL OF
VETERINARY MEDICINE
PREVALENCE OF BOVINE MASTITIS AMONGST
SMALL HOLDER DAIRY HERDS IN KENYA
Vol. 59 (1-2)
2004
Anakalo Shitandi1*, Gathoni Anakalo1, Tura. Galgalo2 and Milcah.
Mwangi2
1. Microbiology laboratory, Dept of Dairy Science, 2. Dept of Biomedical
Sciences,
Egerton University Njoro, P.O. Bo 536 Njoro 20107 Kenya.
E-mail: ashitandi@eudoramail.com
*Corresponding author.
Summary
This study investigated the current status of inflammatory mastitis in smallholder
dairy bovine udders in the Rift Valley of Kenya over a seven-month period. The
prevalence of mastitis was assessed by the results of physical examinations of the
mammary gland by palpation, and by bacteriological evaluation of milk secretion
from a total of 989 quarters. The samples were randomly collected from udders
apparently normal and those affected by mastitis from 250 cows (87 herds) in
Elburgon, Njoro, Nakuru, Naivasha and Nyahururu of Kenya. The prevalence of
clinical mastitis was 19.6 % (n=49) at cow level. The prevalence of major pathogens
isolated from 989 quarters was 34.2% for Staphylococcus aureus, 21.1% for
coagulase negative staphylococci; 16.4% for Streptococcus spp and 7.3 % for
Escherichia coli. There was a significant (P < 0.05) difference in bacterial organisms
isolated in udders affected by mastitis than in normal healthy udders. The prevalence
of bovine mastitis in the smallholder dairy herds was high as to cause substantial
economic loss to farmers. It is concluded that microbiological and epidemiological
surveillance is necessary for effective treatment and control of the disease. Hence,
prevention and control of mastitis needs to be instituted in all the herds.
Introduction
Mastitis is an inflammation of the mammary glands of dairy cows
accompanied by physical, chemical, pathological and bacteriological changes
in milk and glandular tissue (1, 2). The disease, which is common in dairy
cows, causes significant losses to the dairy industry and affects milk hygienic
and sanitary features (3, 4, 5). Mastitis is also of nutritional and great
technological significance in milk processing as valuable components like
lactose, fat and casein are decreased while undesirable components like ions
and enzymes are increased (6). The disease is usually classified as subclinical, acute, subacute, chronic and gangrenous based on aetio-pathological
findings and observations (7).
Bovine mastitis is known to be a problem in Kenyan dairy herds from previous
studies (8, 9, 10). The current prevalence of bovine mastitis has however not
been estimated in Kenyan smallholder dairy cattle (with a size of 1-5 animals)
in the Rift Valley region. This is despite the importance of this sector and
region as evident from production statistics where over 70% of the total milk in
Kenya is known to come from smallholder dairy farmers (11). The sectors
animals (Bos Taurus and their crosses with Bos indicus) at various grading
levels, average milk yields estimated at 1300 liters per lactation (12) from
approximately 3 million dairy cattle (11).
There is therefore a need to assess the current status of inflammatory
mastitis, its clinical prevalence and causal agents involved amongst this
sector in Kenya. This study aimed at obtaining the information from
smallholder farms within milk producing regions in the Rift Valley of Kenya to
enable assessments of potential interventions in the sectors production
system.
Methods
Animals: Two hundred and fifty lactating cows were examined from 87 dairy herds
in different smallholder farms in six regions (Elburgon, Njoro, Nakuru, Naivasha,
Nyahururu and Naivasha) during November 2001 — June 2002. The areas from the
Rift Valley represent major milk producing regions in Kenya. The breeds sampled
were mainly Bos Taurus and their crosses with Bos indicus at various grading levels.
Random number sampling was used in selecting the cows on the farms visited.
Information on age, parity, lactation stage and previous history of mastitis was
gathered. Cows were kept in semi-confinement open housing and milked twice daily.
Feeding was based on forage diets largely from Napier grass fodder, Kikuyu grass,
crop residues and occasional supplementation with dairy meal during milking time.
Sampling: Visual observation and palpation of the mammary gland halves and
macroscopic examination of the milk was undertaken on all the cows in the study.
The cases of clinical mastitis encountered were studied in detail, the following being
recorded for each cow: age, clinical state (acute, subacute, chronic and gangrenous).
They were then classified as follows:
Acute mastitis: Severe inflammation of the mammary gland without any marked
systemic reaction.
Subacute mastitis: Inflamablemation of the mammary gland with abnormalities in
milk.
Chronic mastitis: Inflammation of the mammary gland, with little change in milk
where the gland was either enlarged or reduced in size.
Gangrenous mastitis: Characterized by swollen mammary gland, cold to the touch
and bluish-black in color. The affected skin area peeled off, with oozing of serous
fluid. Milk was bloody and watery.
Prior to quarter sampling the teat ends were cleaned and rubbed with cotton
moistened in 70 % alcohol, initial streams of milk were discarded and approximately
5 ml of foremilk collected into 10-ml polythene tubes kept on ice. A portion of each
quarter milk sample was inspected for clots, discoloration or wateriness before adding
the California mastitis test (CMT) reagent. The rest of the milk was immediately
transported cooled (4oC) to the Microbiology Laboratory, Egerton University Njoro
for bacteriological examination.
California Mastitis Test (CMT): The CMT reagent (DeLaval, Wroclaw, Poland)
and the method were used alongside the physical examinations and the test was
carried out as described (13). Reactions were graded 1, 2, 3, 4, or 5 according to the
Scandinavian recommendations (14).
Bacteriological diagnosis: Isolation and identification were carried out according to
the Scandinavian recommendations on examination of quarter milk samples (14,15)
In brief, immediately after delivery, the milk samples were inoculated on blood agar
plates (Becton Dickinson and Company, USA), which were divided into four sections.
A disposable culturing loop (10µl) was dipped into the milk sample and a total of 6-8
lines made in one agar section by turning the loop once between the streaking lines.
Each quarter milk sample (10µl) was thus streaked in one section of the plate as a line
culture. Samples were cultivated under aerobic conditions for 24 - 72 h at 37oC and
examined for bacterial growth. Pure cultures were further examined for
morphological, staining and cultural characteristics, and for biochemical reactions
according to standard keys (15). Staphylococci were studied in particular for
haemolysis and coagulase production (tube method using oxalated rabbit plasma in a
1:10 dilution in a nutrient broth incubated at 37oC and inspected at 30 min intervals
for 5-6 h for clot formation). A positive coagulase test was judged as any degree of
clotting from a loose clot suspended in plasma to a solid clot (16). For the
Staphylococcus aureus counts - 0.1 ml of the sample was inoculated in duplicate, at
the appropriate dilutions, on Baird-Parker Agar, and incubated at 35 ± 1oC for 24-48
h before colony counting. In cases of mixed growth, a new quarter sample was taken
and re-examined.
Quarters were classified as not infected (NI) if no organisms were isolated, infected
with major pathogens (MAP) if Streptococcus agalactiae, other Streptococcus species,
Staphylococcus aureus, and Escherichia Coli were isolated, and infected with minor
pathogens (MIP) if coagulase — negative staphylococci were isolated. Quarters were
also classified as “normal” if no organisms was isolated, the udder had no injuries or
indurations, the appearance of the milk was normal, and no previous history of
mastitis was recorded and “abnormal” otherwise. Samples with unspecified mixed
cultures were considered contaminated and thus excluded from subsequent analysis.
Statistics: The level of significance between the occurrence of each of the isolated
organisms in udders with mastitis and udders without mastitis (control) was
determined using the ?2 test and all values where P < 0.05 was considered as
significant.
Results
Prevalence of clinical mastitis
A total of 250 cows (989 quarters) were examined of which 11 cows (Seven from
apparently mastic and four from apparently non mastic cows) had lost a quarter each.
Forty-nine cows (19.6%) displayed evidence of clinical mastitis at the cow level. The
number of quarters affected was: left fore, 51; right fore, 57; left hind, 42; right hind,
39. There was no significant difference (p < 0.05) in the number of quarters affected
in relation to their anatomical positions.
The age of affected cows ranged from 2 to 10 years of which 19.6% had clinical
infections from the total of cows examined (Table 1). With regard to the clinical state
of the mammary gland, there was no statistical difference (P > 0.05) in age
distribution with respect to the form of clinical mastitis.
Table 1. Mastitis cows (n=250) from the Rift Valley Highlands, Kenya, grouped
according to the clinical state of the mammary gland in various age groups.
Clinical
state
of
the
Prevalence
10-Aug
7-May
4-Feb
mammary gland of cows
n(%)
22 (8.8)
9(3.6)
6(2.4)
7(2.8)
Acute
14(5.6)
7(2.8)
5(2)
2(0.8)
Chronic
9(3.6)
4(1.6)
3(1.2)
2(0.8)
Subacute
4(1.6)
1(0.4)
3(1.2)
0(0)
Gangrenous
49(19.6)
21(8.4)
17(6.8)
11(4.4)
Total per age group
The average milk production per quarter was 1.83+/-0.12. The results for the CMT scores are shown in
table 2.
Table 2. CMT scores of milk samples from 989 quarters in the dairy herds.
CMT score
1
2
3
4
5
Number (%) of samples
436(44.1)
192(19.4)
146(14.7)
64(6.5)
151(15.2)
The frequency of bacterial species cultured from each of the quarter milk samples from the
201 non-mastitic and 49 mastitic udders is shown in Table 3.
Table 3. Frequency of various types of bacteria isolated from apparently affected
(n=191) and apparently unaffected milk of cows (n=798).
Bacterial isolates
Mastitic milk n(%)
Staphylococcus aureus 58 (30.3)
Coagulase
negative
staphylococci
34(17.8)
Streptococcus spp
39(20.4)
Escherichia coli
20(10.5)
Actinomyces spp
10 (5.2)
Salmonella spp
1(0.5)
Pseudomonas spp
0(0)
Enterobacter spp
0 (0)
Proteus
0(0)
Total
recovery
of
bacteria
162(84.8)
Apparently normal milk n(%)
280(35.1)
Prevalence n(%)
338(34.2)
175(21.9)
123(15.4)
52(6.5)
12(1.5)
12(1.5)
12(1.5)
8(1.0)
16(2.0)
209(21.1)
162(16.4)
72(7.3)
22(2.2)
13(0.2)
12(1.5)
8(1.0)
16(1.6)
690(86.4)
852(86.1)
Negative
culture/No
growth samples
29(15.2)
108(13.5)
137(13.9)
Discussion
The present study was carried out on selected herds located in the Rift Valley of
Kenya to determine the true infection status of cow/quarters by microbiological
analysis (culturing) of aseptically taken milk samples. This area has numerous
smallholdings (farms) and a small number of larger herds. The standard of milking
hygiene was poor on the majority of the farms sampled. Preventive measures, such as
the use of udder disinfectants, post-milking teat dipping and dry cow therapy, were
observed to be infrequent in these herds. In the majority of the herds (74%) there was
no surveillance program in place for mastitis.
Staphylococcus aureus and CNS were the major mastitis-inducing pathogens
detected in this study (Table 3). This finding was similar to reports from earlier
investigations in other regions in Kenya (9, 10, 17) and Tanzania (18) indicative of
the commonness of S. aurues mastitis in the small dairy sector. The results may be
suggestive of a possible development of resistance from prolonged and indiscriminate
usage of beta — lactam antibiotics as evident from a previous study (19).
Because the quality of the milk cannot be improved following extraction from the
cow, production of high quality milk requires an efficient mastitis control program.
Cows with a high prevalence of mastitis as in this study are incapable of producing
high quality milk until the inflammation and infection in the udder are brought under
control. This has severe economic implications for the milk producer, as the milk is
no longer marketable and other animals are easily infected. Treatment and decrease in
milk volume also cause considerable losses per animal.
Systematic records regarding the epidemiology of cow mastitis, status of infection,
treatment patterns would provide useful management information to the producer,
veterinarian and other mastitis control team members. This has been evident from
countries where records have been documented regularly internationally such as in
Norway (20) since 1975, 1982 in Finland (21) and 1984 in Sweden (22). There is thus
a need to routinely investigate and record the epidemiology of bovine mastitis and
antibiogram sensitivity of bacterial isolates from the smallholder sector in Kenya.
Acknowledgements
We are gratefully to the Swedish Institute (SI) for financial assistance. We thank
Emil Olden and Claes Ericksson (SLU-Uppsala) for their input in the laboratory
analysis and are grateful to dairy owners and herders in the Rift Valley province for
their cooperation. Special thanks are extended to Professor Åse Sternesjö (SLU) and
Dr.Carlos Concha of the Swedish Veterinary Associaition - Uppsala for technical
advice and guidance. We thank Mrs Lotta wall for her coordination of supplies from
Sweden to Kenya and Professor Mahungu Symon for permission to use the
microbiology laboratory at the Guildford Institute — Egerton University Kenya.
LINKS TO OTHER ARTICLES IN THIS ISSUE
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