Diseases transmitted through milk
A- Bacterial diseases
1- Tuberculosis ( T B) :
Tuberculosis has been recognized as one of the
most important and serious human infectious
diseases .
Causative agent :
There are two types of tuberculosis :
a- Pulmonary type of tuberculosis : it is
caused by human type i.e. Mycobacterium
tuberculosis which affect the respiratory tract.
It is pathogenic for man.
b- Non pulmonary type of tuberculosis . It is
pathogenic to cattle and man . caused by
Mycobacterium tuberculosis bovis which
Sources of Mycobacteria in Milk
1- Milk animal infected udders( Bovine type).
2- Infected feed.
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3- Wash water.
4- Handlers personnel.
5- Environment:
Dust,fodder, Manure.
Tuberculosis mastitis :
A symptomatic excretion of tubercle bacilli in
milk cans occur from infected animals.
Tuberculous mastitis show pronounced and
characteristic changes to the milk and the
udder . The milk may contain enormous
numbers of bacilli which may enter the milk
directly . When the udder tissues are
extensively involved, firm swelling may be
observed and exhibit small nodules.
Pulmonary Tuberculosis :
Manure of animals must be considered as a
very common source of infection of milk when
animals are affected with pulmonary farm of
the disease. When open lesions are present in
the lungs. the infected material containing a
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large number of tubercle bacilli may be
coughed into the mouth and the cows do not
expectorate but swallow the sputum and in this
way a large number of bacilli pass through the
alimentary tract , The stable air and dust
should be considered a less important for
source of infection, although particles of
sputum and moisture may be expelled into the
stable air by the coughing of tuberculoses
cows during milking, milk become
contaminated with my bacterium bovis more
commonly through the udder and from the
manure of infected animals that clings to the
udder and sides of the cows not properly
cleaned before milking. Also milk may
become infected from fresh manure splashing
from the floor into the milk pail or into other
milk utensils.Asymptomated from infected
animal with military TB i.e. open generalized
T. B
Infection with different types of tubercle
bacilli :
1- Human type :
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Human type tubercle bacilli ( Mycobacterium
tuberculosis ) may gain direct access to milk
from milkers and other handlers and may
reach the consumer in the same way as other
milk-borne pathogen if they are not eliminated
by adequate heat treatment.
II- Bovine type:
Milk animals other than cattle are also affected
with TB mainly by bovine type .
Prevention and control of TB :
1- All cattles should be subjected to tuberculin
skin test to find whether particular animal has
this disease or not .
2- Tuberculous cattle should be slaughtered .
3- Proper heat treatment of milk and milk
products should be practiced. The traditional
habit pasteurization should be employed to
destroy these pathogens and render milk safe
for consumption .
4- Overcrowding must be avoided .
5- Living conditions should be improved .
6- Infected individuals should be isolated.
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7- Tuberculous patients should be prohibited
from handling cattle and milk .
8- Proper disinfection of udder clothes,
Utensils etc.
9- Vaccination of uninfected individuals .
10- Open air sheds.
11- Compulsory notification of all cases of
tuberculosis .
Testing the cows with Tuberculin and
slaughtering of reactors and pasteurization of
milk has substantially reduced the level of
human infection due to Mycobacterium bovi.
BRUCELLOSIS
A bacterial disease of animal origin. In animal
it causes " infectious abortion". It is one of the
common milk –born diseases.
Causative organisms:
Three principal species of Brucella are
responsible for Brucellosis.
Causative organisms :
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Three principal species of Brucella are
responsible Brucellosis:
Brucella Melitensis ( in goat ). Brucella abotus
in cattle
( Bovine type ) , Brucella suis ( in hogs).
All the three species can infect man and are
excreted in milk of dairy animals.
Theses organisms are secreted into milk
through infected udder.
Sources of pathogen in milk and milk
products:
1- Diseased animals have been shown to
excrete the causative organisms in their milk .
2- Environment is also one of the sources of
contamination.
3- Personal handling milk and animals are also
potential sources.
Prevention and control:
The following preventive and control
measures can be used for minimizing the
incidence of brucellosis through milk.
1- Eliminating the disease in animals by
segregation of the infected herds to avoid cross
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infection to the healthy herd and, if possible
the infected animals should be slaughtered.
2- The herds should be preferly vaccinated
against the disease.
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3- Adequate heat treatment ( Pasteurization )
should be given to milk for the destruction of
the causative organisms .
Diphtheria
It is a bacterial disease of human origin, the
main cause of the disease appears to be poor
sanitary conditions at the levels of production
and processing of milk .
Causative organism or agent :
Corynebacterium diphtheria is the causative
agent of diphtheria. The organism is usually
found in respiratory tract of infected or healthy
carriers. It may also be associated with
wounds on the teats or udder of the cow where
this may cause mastitis.
Source of pathogenic :
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Milk an be infected chiefly through the
following sources:
1- Handlers human carriers who may sneeze or
cough over milk or who use their fingers
contaminated with their nasal discharge.
2- Animal: infected animals may also carry
the organism in the wounds of the teats or in
the udder of the cows from where it may enter
into milk .
3- Environment : air in vicinity of dairy
environment may get contaminated through
sneezing and coughing of the individuals .
Theses unhygienic habits throw the causative
organisms into the environment in the form of
aerosols which may land into milk.
4- Contaminated bottles : milk handlers
carrying the causative organisms of diphtheria
may also pass on the organisms to milk bottle
from where the organisms may reach milk .
Prevention and control :
For prevention and control of the disease the
following precaution are required to be taken :
1- Adequate heat treatment will destroy the
causative organism.
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2- The infected persons carrying the disease
organisms should not be allowed to handle
milk and milk products during production and
processing.
3- The unhygienic practices pike sneezing and
coughing by the dairy personnel should be
avoided.
4- Proper vaccination of the individuals
against the disease is very efficient
prophylactic measure.
4- Anthrax
A bacterial disease of animal origin . It is
acute infectious disease of cattle. The
incidence of milk-borne anthrax are very rare
and it is not so much prevalent as compared to
meat- borne anthrax for the following reasons
:a-Bacilli anthracis can pass from the blood of
infected animals into their milk and such
excretion occurring just shortly before the
death of animal.
b- The milk secretion is suppressed,i.e It
volum is to reduced and milk is altered in it’s a
appearance that milk is not likely to be
consumed.
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Sources of pathogen in milk and milk
products :
1- Infected animal : the discharges and other
secretion of the bacillus anthracic spores into
clean milk from the surrounding of the dairy
farm .
Prevention and control :
The following measures are adopted for
controlling the disease :
1-Milk from infected animals should not be
used.It should be excluded from the general
milk supply.
2- Killing and burning of the a affected
animals .
3- Proper sanitation of the dairy environment.
4- Proper vaccination of the dairy herds.
5- The discharges of the infected animals
should be properly disinfected by ( 10%)
NAOH.
B- Rickettsial diseases
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Like bacterial pathogens, some Rickettsia can
also produce diseases which can be
transmitted through milk and milk products.
Since Rickettsia are resistant toward heat. The
most commonly occurring rickettsial disease
through ingestion of contaminated milk
product is Q-fever .
Q-Fever
It is Rickettsial disease of animal origin Qfever is world wide disease and is caused in
man by rickettsia, namely Coxiella burnetti,
raw milk is commonly implicated as a vehicle
for the transmission of disease.
Sources of causative agent:
Coxiella burnetii are shed in the placental
tissues, uterine discharges, milk, urine and
faeces of the infected cows, mostly, human
infection is by inhalation of infected dust of
the vaginal or faecal materials. Infected cattle
continue to excrete the organisms in their milk
for a long time . So oral infection through
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drinking raw milk may also occur. Also source
of infection.
The infected udders and milk do not show any
abnormality although infected cattle continue
to secrete coxiella can also cause mastitis in
cows .
Prevention and control:
1- A dequate heating of milk and cream .
2- Calving and lambing sheds should be away
from the milking sheds and dairy.
3- Recontamination of heat treated milk with
dust and discharge should be prevented .
4- Animals should be properly vaccinated.
5- Control on import of domestic animals .
C-
Viral diseases :
Some viral diseases can also be transmitted
through milk and milk products but viruses
don't multiply in milk . The diseases which
merit special consideration are :
1- Polio, 2- Infectious hepatitis, 3- Enteric
fever, 4- Tick borne encephalitis, 5- Foot and
mouth disease ,6- Rabies,7- Pox.
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1- Entero- viruses :
Entero-viruses are a group of viruses which
can cause severe epidemics of summer
diarrhea in infants and children on ingestion of
contaminated milk and milk products.
Poliomyelitis :
It is viral disease of human origin, and like any
other common diarrhea disease that occurs
commonly in summer season.
Sources of the pathogen :
1- Person to person contact is the primary
mode of spread of theses viruses .
2- Flies may also serve as the vectors for the
spread of the disease.
3- Faecal contamination of water and milk
may also introduce polio viruses into the
consumers.
4- Milk handlers.
Prevention and control :
1- Milk should properly pasteurized .
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2- Hygienic measures should be followed
strictly to avoid faecal contamination.
3- Infected handlers should not be allowed to
handle milk and milk products.
4- Immunization with immune serum or
pooled Gamma-globulin is also effective in
preventing disease .
5- Proper vaccination of the children confers
protection against the disease.
2- infectious hepatitis :
A among the various viral diseases , infectious
hepatitis ( Jaundice) is considered as one of
the most serious human viral diseases for
which milk may be the important vehicle of
transmission. The illness is also known as
hepatitis .
Source of pathogen :
Some major sources of entry of infectious
hepatitis virus into milk are listed below :
1- Milk handlers : Since disease spreads
through person to person contact. The
milk handlers suspected of carrying the
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causative organisms are an important
source of contamination into milk .
2- Water supply : Defective water supply
in a milk plant may also introduce the
causative agent of this disease into milk .
3- Dairy environment : The polluted
environment in the vicinity of milk plant
or distributing center may also
contaminate milk.
Prevention and control :
The following preventive measures can be
take to minimize the incidences of
infectious hepatitis through milk .
1- Proper sanitary conditions should be
maintained during production and
processing of milk .
2- Infected persons should not be allowed
to handle milk.
3- The faecal contamination of water
should be avoided.
4- Infectious hepatitis A can be prevented
by passive immunization, included by
injecting pooled human Gamma globulins.
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5- A adequate heat treatment of milk is
likely to inactivate the virus.
3- Tick-borne encephalitis :
It has been found to be another type of
animal , viral illness occurring through
milk and milk products . The causative
agent of the disease is the group B of
Arbo-viruses. The virus is inactivated on
pasteurization of raw milk . Hence ,the
presence of the virus in pasteurized milk is
due to its recontamination with the virus.
Sources :
Human infections occur either directly
through tick bites or by drinking
contaminated milk not given adequate heat
treatment.
Prevention and control :
1- A adequate heat treatment .
2- Immunization of milk animal by
vaccine.
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4- Food and mouth disease( FMD)
Food and mouth disease FMD is a highly
contagious viral disease of livestock.
Sources of causative agent :
In animals the virus is present in the fluid
of the vesicles (blister) in the mouth
,nares,muzzle,feet and teats. Milk becomes
infected due to the repturing of the
vesicles on the teats and udder or due to
faulty milking. The virus may gain
entrance to the saliva,faeces and urine
which contaminate the milk .
Lesions some time occur on the udder
which may lead to highly contaminated
milk. While the virus is present in the
blood ( Viraemia ).
The disease in man may be caused by
direct contact with diseased animals or by
ingestion of infected dairy products. Milk
or milk derivatives are one of the means of
spreading FMD from one farm to another .
Prevention and control :
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1- Milk from infected farm should be
adequately heated.
2- Milk from suspected animals should be
discarded.
3- Pasteurization of milk should be proper.
4- Proper vaccination of the dairy herds
should be carried out to confer protection
against the disease.
5- Animal should be thoroughly examined
to ensure that they do not carry any
disease or disease causing organisms .
6- Suspected animals should be
quarantined immediately and the premises
should be disinfected,sodium hydroxide
(2%),sodium carbonate (4%), citric acid
(0.2%) in effective disinfectants.
5- Cow Pox :
Cow pox is a mild form of small pox,
naturally occurring disease of cattle
characterized in the acute form by a
vesicular eruption on the udder and teats.
The infection spreads slowly throughout
milking herds.
Source of infection to man :
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1- Man may become infected with painless
but itchy purplish red nodules that are
generally present on the fingers or hands.
2- It is occupational disease, mainly seen
in dairy farm workers.
3- The disease is contracted by direct
contact with papules on teats or udder.
4- Milk becomes infected due to the
rupturing of the vesicles on the teats or
udder during milking and the virus may
gain entrance to the milk from the fluid of
the vesicles.
5- Infection of non vaccinated children
may be caused be ingestion pf infected
milk which causes gastro intestinal
disturbances .
Prevention and control :
1- Control of infection within the herd is
difficult and depends essentially on
hygienic measures, such as treat dipping to
destroy the virus and prevent transmission.
2- Proper vaccination of the dairy herds
should be carried out to confer protection
against disease.
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3- Outbreak control by isolation of
infected animals.
4- Milk should be properly pasteurized to
inactivate the viruses.
Lecturer
Dr. Akram Motlak Siwiah
Department Public Health
College of veterinary Medicin
Uneversity of Kufa
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