Locally detergents can help African farmers detect Mastitis. On-farm photos: ILRI.

A simple test to detect disease in African dairy cattle

Detergent is a key ingredient in the California Milk Test, a long-established method to test for Mastitis. This study determined which locally available detergents could help farmers in Nigeria and Ethiopia quickly and cheaply detect the disease.

By Jack Rust

Mastitis is regarded globally as the most prevalent and economically important infectious disease in dairy cattle.  While clinical mastitis can be visibly diagnosed and treated on routine physical examination, subclinical mastitis – which may not yet present symptoms – often remains undetected.  An array of causative pathogens can be involved, entering the teat canal and multiplying in the udder, causing inflammation of the mammary gland.  Due to the infectious nature of mastitis-causing pathogens, it is important to detect cases of subclinical mastitis in order to maximise cow health and well-being, as well as maintaining herd health and profitability.

In Ethiopia and Nigeria, dairy cattle are essential contributors to the national economy, yet the productivity and profitability of the dairy subsector remains below potential in both countries.  Subclinical mastitis is considered the most damaging and expensive due to the challenge in early detection, resulting in economic losses due to reduced milk quality and quantity, veterinary costs, culling and deaths.  Although studies on the prevalence of mastitis in both Ethiopia and Nigeria are lacking, the FAO (2014) found 78% of milk loss in Ethiopia was as a result of mastitis at a cost of approximately USD $38 per cow (PDF).

The California Milk Test (CMT) is an inexpensive, easily-applicable, cow-side test that allows for the subjective estimation of the Somatic Cell Count (SCC) present in milk as an assessment of the probability and severity of intramammary infection. The CMT involves combining milk with a testing reagent (containing anionic-surface-active agents), which dissolves somatic cell walls, releasing DNA, causing agglutination to give varying degrees of a ‘slimy’ appearance. The extent of the reaction increases with the SCC and the degree of visible agglutination can be subjectively scored based on an ordinal scale and used as a qualitative test to estimate the SCC of milk samples.

In the UK, an accepted homemade detergent-based CMT reagent comprises of 40ml Fairy Liquid to 160ml water, with 1ml dark food colouring to enhance visualisation (Leach et al., 2008).  We therefore investigated if commercially-available detergents in Ethiopia and Nigeria can be used in the CMT to reliable show high SCC (>400,000 cells/ml).

We cannot assume domestic detergents available in Ethiopia and Nigeria have an equal concentration of anionic-surface-active agents. Therefore, this study undertook a series dilution test to determine the most effective concentration of each detergent for visualising high SCC.

How the study was done

We analysed six commercially-available detergents from Ethiopia (Princess, Rotana and Shagan) and Nigeria (Sunlight, Morning Fresh and Mama Lemons), and created five different dilutions for each detergent, with 1ml food colouring from Ethiopia/Nigeria depending on the detergent country-of-origin.  All dilutions were then tested with 20 quarter milk samples (5 low SCC and 15 high SCC) and the optimal dilutions for each detergent that achieved results most similar to the UK CMT were then taken forward into a validation study to verify that they reliably indicate high SCC.

Results

All Ethiopian detergent-based CMT reagents proved less effective than the UK CMT. However, ‘Shagan’, at a dilution of 55ml detergent to 145ml water with 1ml of indicator, proved the most effective at indicating high SCC. It proved to have the highest sensitivity (75.6%, CI% 63.9-86.3) and negative predictive value (NPV) (84%), and therefore is the best at identifying cows of likely high SCC. Therefore, we promote its use in the CMT as a cost-effective alternative to the UK commercial CMT.

All Nigerian detergent-based reagents proved more effective than the Ethiopian reagents, with ‘Sunlight’ even outperformed the UK commercial CMT reagent at identifying high SCC in milk when at a dilution of 70 ml detergent to 130 ml water with 1 ml indicator. Sunlight proved the highest sensitivity (80.8%, CI% 68.1–89.2), and NPV (88%), and therefore, this study recommends its use in the CMT to identify high SCC.

There were certainly challenges in conducting this study throughout the COVID-19 pandemic: farms were reluctant to have external personnel for sampling, likewise vet practices were only open to emergencies and so unavailable to aid sample collection.  Additional operators were required to test the milk samples; however, this was hard to achieve in compliance with social distancing regulations.  Despite all the challenges, this project has personally been incredibly rewarding and an opportunity to further my interests in global health, agricultural development and food security.

Conclusions and next steps

This study supports the use of the detergent-based CMTs to improve the health and wellbeing of Ethiopian and Nigerian cattle as a cost-effective, easy-to-perform way of diagnosing mastitis on farm, in real time.  This facilitated the control and management of mastitis to increase the quantity and quality of milk, and improve the economic value of the dairy subsector.  This research is contributing to a larger ongoing study into mastitis in both countries, and will be used to produce educational pamphlets and videos to promote the CMT for the control and management of mastitis, for the benefit of Nigerian and Ethiopian cattle and people.

Similar studies to develop CMT equivalence test in Sri Lanka are being planned. If you are working on mastitis management in another country and wish to develop a locally made CMT for your local market, please get in touch.

Read the full study:

Rust JD, Christian MJ, Vance CJ et al. A study of the effectiveness of a detergent-based California mastitis test (CMT), using Ethiopian and Nigerian domestic detergents, for the detection of high somatic cell counts in milk and their reliability compared to the commercial UK CMT. Gates Open Res 2021, 5:146 (https://doi.org/10.12688/gatesopenres.13369.1)

 


Jack Rust is completing a Veterinary Medicine BVSc and Global Health BSc at the University of Bristol. He undertook this study for SEBI-Livestock with funding from MSD Animal Health Research Bursary for veterinary students

 


Vanessa Meadu, Communications and Knowledge Exchange Specialist, SEBI-Livestock
Page created: 31 May 2022 Page last reviewed: 21 Jun 2024