Milk Product Image

MILK BORNE DISEASES

The importance of milk in our diet is well established as it is considered as the best, ideal and complete food for all age groups. However, in spite of being so, milk can also serve as a potential vehicle for transmission of some diseases under certain circumstances. Moreover, by virtue of possessing almost all the essential nutritional factors, milk can also serve as an excellent source and protective medium for certain microorganisms, which may include potential pathogens capable of causing various health problems to the consumers.

In this way, milk may serve not only as a potential vehicle of transmission of disease causing organisms, but it can also allow these pathogens to grow, multiply and produce certain toxic metabolites, thereby making itself an extremely vulnerable commodity from the public health point of view.

A variety of pathogenic organisms may gain access into milk and milk products from different sources and cause different types of food-borne illnesses. Milk and milk products may carry organisms as such or their toxic metabolites (poisons) called ‘toxins’ to the susceptible consumers. Ingestion of toxins already synthesized in the food i.e., pre-formed brings about poisoning syndromes in the consumers.

This is called ‘food intoxication’ and the toxins affecting the gastro-intestinal tract are called enterotoxins. Whereas the ingestion of viable pathogenic bacteria along with the food leads to their implantation and establishment in internal organs. This is called ‘food infection’. There are yet other types of organisms, which can infect intestine when ingested along with the food and produce toxins in situ to bring about symptoms of poisoning. This situation is called ‘toxi-infection’.

These three categories are better covered by the term food-borne infections and intoxications. Apart from these food-borne illnesses, a number of other types of diseases whose etiological agents may be bacteria, fungi, rickettsiae and viruses can also be spread through milk and milk products. The microbiological health hazards arising from the consumption of contaminated high risk foods like milk has grown in recent years and has resulted in national and international intensification of food hygiene programs.

Although the occurrence of incidences of food-borne illnesses has been considerably reduced in most of the developed countries chiefly due to adoption of strict microbiological quality control and sanitary practices during the production, processing and distribution of milk and milk products, the situation continues to be grim in developing countries where such practices can not be followed. This problem is aggravated when heavy expansion of dairy industry in the third world countries and this increases the risk of milk-borne intoxications and other illnesses.

Common milk-borne infections, intoxications and toxi-infections

Sl. No.	Type of milk borne disease	Causative agent	Disease/disorder
1	Food infection	Salmonella typhi and related species Shigella dysenteriae Streptococcus sp. (enterococci)	Typhoid, Salmonellosis (food poisoning) Shigellosis (dysentery) Septic sore throat, Scarlet fever, food poisoning
2	Food intoxication
	Bacterial	Staphylococcus aureus Clostridium botulinum	Food poisoning Botulism (food poisoning)
		Escherichia coli Vibrio cholerae	Summer diarrhea Cholera
	Fungal	Aspergillus flavus Other toxigenic mold sp.	Aflatoxicosis Mycotoxicosis
3	Toxi-infection	Bacillus cereus Clostridium perfringens	Food poisoning Gas gangrene
4	Other milk-borne disorders (uncertain pathogenesis)	Aeromonas sp. Proteus sp.	Food poisoning Food poisoning
		Klebsiella sp. Pseudomonas sp. Citrobacter sp.	Food poisoning Food poisoning Food poisoning
5	New emerging pathogens	Yersinia enterocolitica Campylobacter jejuni Vibrio parahaemoyticus	Diarrhoeal diseases Diarrhoeal diseases Diarrhoeal diseases
		Listeria monocytogenes	Listeriosis
6	Other milk-borne diseases:
	Bacterial	Mycobacterium tuberculosis	Tuberculosis
7	Milk-Borne Diseases : Infections, Intoxications and Toxi-infections
	Bacterial diseases	Brucella abortus Corynebacterium diphtheriae	Brucellosis Diphtheria
		Bacillus anthracis	Anthrax
	Rickettsial diseases	Coxiella burnetti	Q fever
	Viral diseases	Entero viruses Infectious hepatitis virus Tick-borne Encephalitis Virus Foot and Mouth Disease virus (FMD-virus)	Enteric fever Infectious hepatitis Tick-borne Encephalitis Foot and Mouth Disease (FMD)

The pathogenic organisms may be derived chiefly from:

(1) Dairy animals
(2) Human handlers
(3) Environment

(1) The health of dairy animals is a very important consideration because a number of diseases of cattle including Brucellosis, Q fever, Salmonellosis, Staphylococcal and Streptococcal infections and Foot and Mouth Disease (FMD) virus may be transmitted to man through the consumption of milk. The organisms of most of these diseases may be transmitted to milk either directly from the udder or indirectly through the infected body discharges, which may drop, splash or be blown into milk.

(2) The diseased persons may transmit disease like typhoid fever, scarlet fever, diphtheria, septic sore throat, and infantile diarrhea by contaminated hands or by coughing, sneezing and talking.

(3) Dairy and farm environment may also introduce a variety of pathogens into milk and milk products at different stages of production and processing. Some common air-borne pathogens include Group A streptococci, Corynebacterium diphtheriae, Mycobacterium tuberculosis, Coxiella burnetti and some viruses of respiratory origin. Water, fodder and unhygienic conditions at farm and plant level may also contribute pathogens to milk.

Prevention of milk-borne diseases is one of the most important problems of public health. Success in controlling a disease can be maintained only by the constant vigilance over the health of the cow udder until it reaches the mouth of the consumers.

Animal diseases transmitted to human beings through milk