Occurrence of High Udder Infection Rates in Dairy Cows in Ungunja Island of Zanzibar, Tanzania

 

G. K. Gitau*

M. Waridi†

H. A. Makame†

M. M. Saleh†

R. A. Muhamed†

A.P. Mkola†

M. A. Haji†

 

*Department of Clinical Studies, Faculty of Veterinary Medicine, University of Nairobi, Nairobi

†Commission for Livestock, Ministry of Agriculture, Zanzibar, Tanzania

 

KEY WORDS: Mastitis, dairy cow staphylococcus species, infection

Abstract

A 2-week screening was performed in small holder dairy farms in 4 districts of Ungunja Island of Zanzibar in August and September 2002. A total of 128 cows from 49 farms were screened for mastitis using the California Mastitis Test (CMT). Of the dairy cows screened, 63% (80 of 128) were dairy breeds such as Friesian, Jersey, Guernsey, and Ayrshire or their crosses, and 37% (48 of 128) were crosses with the local Zebu cattle. The 128 cows had a total of 506 functional quarters, with six cows having lost one quarter each from either past mastitis or teat obstruction. This left a potential total of 512 quarters.

Of the 506 quarters screened, 32% (162 of 506) were negative on CMT and the remaining 68% (344 of 506) were positive. Of the positive quarters, 16% (82 of 506), 16% (83 of 506), and 35% (179 of 506) were 1+, 2+, and 3+, respectively, on the CMT scale. Of the 189 milk samples cultured, 84% (158 of 189) yielded growth; there was no growth in 16% (31 of 189) of the samples, resulting in a quarter infection rate of 84%. After the cultures were identified through colony characteristics and microscopic examination, 85% (135 of 158) were found to be Staphylococcus species, and the remaining 15% (23 of 158) were Streptococcus species. Both hygiene of the milkers and the farm were thought to be associated with the high subclinical rate of Staphylococcus mastitis.

Introduction

In most countries, surveys indicate that the incidence of mastitis morbidity among dairy cows is about 40%, irrespective of the organism involved, as measured by indirect tests. The quarter infection rate is estimated at about 25%.1^-3 This could be as low as 10% for significant pathogens. The average incidence of clinical mastitis is about 10%. In general, mastitis is not a fatal disease except for acute staphylococcal mastitis in a recently calved cow.4

Although mastitis occurs sporadically, it assumes a major economic importance in dairy cattle. The economic losses associated with mastitis make it the most important disease with which the dairy industry must contend.4 Estimates show that, on the average, an affected quarter suffers 30% reduction in productivity and an affected cow is estimated to loose 15% of its production for the lactation.4

The predominant infection in different countries is from Staphylococcus aureus followed by Streptococcus agalactiae. The former is the most important cause of subclinical mastitis.5 The prevalence and incidence of an individual organism, therefore, depends on a number of risk factors. These factors include the size of the herd and quality of management, especially hygiene and cleanliness of accommodation.4

Two classes of mastitis occur based on the source of infection.4 The first class is contagious mastitis, in which other infected cows are the source of infection. S. agalactiae and S. aureus are common inhabitants of the tissues in cows. The second class is environmental mastitis, in which bedding and other inert objects are the source of infection. Echerichia coli is a common inhabitant of the cows’ environment. Infection occurs via the teat canal for each mammary gland, either from an infected animal or the environment. In dairy cattle, organisms from the infected udder is transmitted to the teat skin of other cows by milking machine liners, milkers’ hands, wash clothes, and other inert materials.4 This study was designed to screen dairy cows in Zanzibar for udder infections followed by culture and identification of some of the organisms.

Materials and Methods

Selection of Study Districts and Farms

Five districts of Ungunja Island of Zanzibar, where dairy farming is concentrated, were selected for this study, which was performed for 2 weeks between August 26 and September 5, 2002. The farmers on the selected farms practice mixed farming, in which dairy farming is combined with growing food crops and horticulture.

A total of 49 farms were selected on the basis of whether a lactating dairy cow was on the farm at the time of the study. The selected farms were distributed in the districts as follows: Western, 11; North A, 2; North B, 10; and Central, 26. From the 49 farms, a total of 128 cows were selected for the study. Most of the dairy cows studied were crosses between various dairy breeds such as Friesian, Jersey, Guernsey, and Ayrshire or their crosses with the local Zebu cattle.

Screening of Udder Quarters for Mastitis

All udder quarters from the 128 cows were screened for potential infection using the California Mastitis Test (CMT). Milk was collected from individual quarters into mastitis paddle wells, ensuring that the first few strips were discarded. Using the CMT test, the results were classified as either negative or positive. The positive samples were further reclassified into 3 classes: 1+, 2+, or 3+.4

From the cows that tested positive by CMT, a convenient sample of 49 cows was selected whose milk was used for laboratory culture. The selection was based on a 2-way criteria: at least one cow from each farm was included and cows with positive 3+ results were considered first. The above was to ensure a fair distribution of farms in the four districts and also increase the chance of isolating organisms from the positive 3+ cases. A total of 189 individual quarter milk samples from 49 cows were collected, with care taken to minimize contamination. About 4 to 5 streams were collected into sterile universal bottles and labeled clearly. The samples were stored in cool boxes with icepacks and transported to the laboratory for culture.

Bacterial Culture and
Microscopic Identification

While in the laboratory, all the milk samples were cultured on Blood agar. A few samples were also cultured on MacConkey agar. The latter were selected conveniently with preference given to those with less than positive 3+ on CMT. All the cultures that yielded growth were first examined and identified through colony characteristics. Thereafter, they were examined under light microscopy using gram stain. Due to unavailability of additional tests, the bacteria were identified to the genus level.

Results

A total of 128 cows from 49 farms were screened for mastitis using the CMT. Of the dairy cows screened, 63% (80 of 128) were dairy breeds such as Friesian, Jersey, Guernsey, or Ayrshire or their crosses, and 37% (48 of 128) were crosses with the local Zebu cattle. The 128 cows had a total of 506 functional quarters, with 6 cows having lost a quarter each through previous mastitis or teat obstruction (Table 1).

Of the 506 quarters screened, 32% (162 of 506) were negative on CMT and the remaining 68% (344 of 506) were positive. Of the positive quarters, 16% (82 of 506), 16% (83 of 506), and 35% (179 of 506) were 1+, 2+, and 3+, respectively, on CMT (Table 1). Of the 189 milk samples cultured, 84% (158 of 189) yielded growth, with no growth in the remaining 16% (31 of 189) (Table 2). The resulting quarter infection rate was 84%. After the cultures were identified through colony characteristics and microscopic examination, 85% (135 of 158) were found to be S. aureus and the remaining 15% (23 of 158) were S. agalactiae (Table 2).

Discussion

The results of this survey showed that there has been steady growth in the number of dairy animals after the eradication of the tsetse fly on the Unguja island of Zanzibar. Trypanosomosis, which is transmitted by the tsetse fly, has been a major constraint to the introduction of exotic breeds of cattle in Zanzibar. This observation shows that the current program of upgrading and introducing new dairy cattle in Zanzibar has been successful.

However, the results further showed that the udder and quarter infection rates in dairy cows in Zanzibar were high compared with those reported elsewhere.4 The quarter infection rates estimated at 68% by indirect method (CMT) or at 84% by direct method (culture) in this study are high compared with reported estimates of 25% and 40% by indirect and direct methods, respectively, in dairy cows in other countries.4 The main organism identified in 85% of the cultures was S. aureus, a principle cause of subclinical mastitis and of contagious mastitis.5 This is in agreement with studies in other countries of the world that show S. aureus to be the predominant infection of the udder. This also concurs that it is the most important cause of subclinical mastitis, followed by S. agalactiae.4

Conclusions

In conclusion, the udder and quarter infection rates in dairy cows on the Unguja island of Zanzibar were very high. Because S. aureus infection comprised the majority of the infection and is also the most important cause of subclinical and contagious mastitis, it was highly likely that hygiene of the milkers and farm was the key contributor to the high infection rates. A controlled study to evaluate the role of hygiene in the milkers and farms is needed. In the meantime, it is highly recommended that a simple, farmer-friendly mastitis control program be introduced to correct the current high udder and quarter infection rates.

Acknowledgments

We are grateful to the International Atomic Energy Agency (IAEA) for funding the work under project URT/5/021. This work was published with the permission from the Commissioner for Livestock, Ministry of Agriculture, Zanzibar, Tanzania.

References

1. Miltenburg JD, et al: Vet Rec 139:204, 1996.

2. Fox LK, et al: J Dairy Sci 78:1619, 1995.

3. Pankey JW, et al: J Dairy Sci 74:1550, 1991.

4. Radistitis OM, Gay CC, Blood DC, Hinchliff KW: Veterinary Medicine: A Textbook of the Diseases of Cattle, Sheep, Pigs, Goats and Horses, 9 Ed. Philadelphia: WB Saunders; 2000.

5. Fox LK, Gay JM: Vet Clin North Am 9:475, 1993.

 

 

Table 1. Results of the California Mastitis Test (CMT) for 128 Cows in Unguja, Zanzibar

 

  CMT

                   

  0              38         36         43         45         162

  1              17         23         22         20          82

  2              22         18         23         20          83

  3              49         49         39         42         179

 

  Total       128       128       128       128        512

 

  *10=negative; 1=1+; 2=2+; 3=3+ on CMT test.

  RFQ, right forequarter; LFQ, left forequarter; RHQ, right hindquarter; LHQ, left hindquarter.

 

Table 2. Results of Bacterial Culture in 128 Cows in Unguja, Zanzibar

 

  Udder              Number           CMT test*                                 No                       

 

  RFQ                   126                    88                   41                  8                       35                         6

 

  LFQ                   126                    90                   44                  4                       35                         9

 

  RHQ                  127                    84                   33                 12                      29                         4

 

  LHQ                   127                    82                   40                  8                       36                         4

 

 

  *10=negative; 1=1+; 2=2+; 3=3+ on CMT test.

  RFQ, right forequarter; LFQ, left forequarter; RHQ, right hindquarter; LHQ, left hindquarter.