Increasing zoonotic milk-borne pathogens: a complex challenge to the

growing dairy industry in Eastern Africa

H. Kirunda, N. Muwereza, T. Kabuuka, S.D. Kerfua, P. Emudong and P.D. Kasaija

African Livestock Conference and Exhibition (ALiCE), June 18th -20th 2014, Speke Resort and Conference Center, Munyonyo, Kampala, Uganda

Livestock farming in Uganda

Many African countries do not have adequate food security, yet some are already weakened by conditions such as:

malaria

HIV/AIDS

Different program are being undertaken to increase livestock production

Although very gradual, some of the Eastern Africa countries continue to achieve increase in milk production

Trend of milk production in Eastern Africa

Source: FAOSTAT, 2014

Supply of whole milk

Source: FAOSTAT, 2014

Export of fresh milk

Source: FAOSTAT, 2014

Livestock farming in Uganda

Efforts to improve food security are threatened by foodborne diseases

Each year foodborne diarrhoeal diseases kill an estimated 2.2 m people especially on the African continent

Eastern and Southern Africa face estimated 1,400m diarrhoea episodes annually

Control of these diseases face challenges of globalization of the food market, climate change and changing patterns of human consumption

Livestock farming in Uganda

Milk is a good medium of growth of pathogens that cause disease in humans

Contamination affects milk safety/spoilage; negatively impacting on growth of developing dairy industries in Eastern Africa

While processing may reduce the level of milk contamination with such agents, milk marketing dominated by the informal sector

Only 10-20% of milk sold is through the formal market chains

Livestock farming in Uganda

Due to lower quality requirements in the informal markets, these markets account for 80% - 95% of milk marketed in the region

Up to 80% of the marketed milk the bulk of the milk is consumed in raw form, yet milk in the region is still highly contaminated

There is high preference for liquid milk in the region except in Ethiopia where bulk of the milk is processed into butter

 

Zoonotic milk-borne pathogens

Common zoonotic milk-borne pathogens:

Brucella abortusMycobacterium bovis

Recently, un common zoonotic pathogens have been isolated in milk of cattle

The paper reviews the recently isolated milk-borne zoonotic pathogens in countries of Eastern Africa.

Milk contamination with B. abortus and B. melitensis Brucella abortus was previously the only pathogen isolated from

milk of cattle, while B. melitensis was known in goats

B. melitensis has been isolated from cattle alongside B. arbutus in Kenya

B. melitensis and B. abortus are all capable of causing human infections, B. melitensis now most common and cause a more serious disease

Rearing small ruminants alongside cattle has previously been associated with infection of cattle with B. melitensis

Brucella organisms are transmitted to humans through direct contact with livestock or by ingestion of unpasteurized milk

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Milk Contamination with Enterotoxigenic E. coli O157:H7

Cattle are the reservoirs of shiga toxin-producing E. coli (STEC) including the zoonotic STEC, EHEC strains

EHEC strains produce diarrhea-causing enterotoxin and among them E. coli O157:H7 is the predominant cause illness

In Eastern Africa, the annual food poisoning cases due to E. coli are between 100,172 in Burundi and 769,248 in Ethiopia

EHEC O157:H7 has not been isolated in a number of countries, but has been isolated in Kenya, Tanzania, Ethiopia and Uganda

At farm level, the degree of E. coli contamination is 2.0 x 106 CFUs/mL, and can increase 150-fold during transportation

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Contamination of milk with Mycobacterium bovis

Bovine tuberculosis is an infectious disease primarily caused by Mycobacterium bovis. Cattle are the primary host of M. bovis

M. bovis is a member of Mycobacterium tuberculosis complex, which also includes M. tuberculosis

There has been persistent isolation of M. bovis from cattle in Ethiopia, Kenya and Uganda

A clonal complex of M. bovis , African 2 (Af2) has been identified to be localized in Eastern Africa region

Represent >70% of the isolates from cattle in Uganda, Burundi, Tanzania and Ethiopia. Has never isolated elsewhere in the world

Infections in man are through consumption of unpasteurized contaminated milk 12

Challenges in control of B. melitensis and B. abortus

Isolation of both B. melitensis and B. abortus in milk of cattle

While serology is the easiest approach to disease detection, no single serological test is reliable for detecting brucella infection

Most of the milk is produced among pastoralist communities where control is most challenging

Several complex risk factors exist and these are tightly linked and intrinsic to the farming practices

Traditional beliefs and practices that interfere with acceptance of disease control measures exist in such communities

Vaccines can induce abortion, have limited ability to prevent infection and seroconversion after exposure 13

Challenges in control of EHEC O157:H7

Colonisation of the gut of cattle by EHEC O157:H7 is not clearly understood

Information on identification and characterization of the non-O157 STEC strains in milk is lacking.

  Non-O157 STEC strains are more difficult to detect in samples

than EHEC O157:H7

Vaccine against EHEC is not currently in use in any of the Eastern Africa countries

Use of PCR requires testing of extracts from primary cultures, which are only possible by use of selective/differential media

STEC strains are becoming resistance of to several antibiotics14

Challenges in control of EHEC O157:H7

Larger herds of bovines have been linked to increased likelihood of occurrence of bovine tuberculosis

Exotic breeds have been reported to have a higher risk of infection with M. bovis compared to the native cattle breeds

The efficacy of promising candidate bTB vaccines are just undergoing evaluation in Eastern Africa

The tests used in detection of M. bovis are slow, cumbersome, unreliable, and time-consuming

Molecular tools have not gained much use in field laboratories and the need for extraction of DNA from primary cultures

The effect and consequences of M. bovis Af2 not understood 15

General challenges to control ofzoonotic pathogens

In Eastern Africa, it is less likely to have appropriate;

1.Disease surveillance system

2.Diagnostic capabilities

3.Research

4.Regulatory framework

5.Programme management

6.Animal identification (traceability)

7.Regional cooperation

8.Social cooperation

Without change, minimising milk contamination with zoonotic pathogens would prove very difficult or almost impossible 16

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