Dairy Microbiology Lecture II

Dairy Microbiology Lecture II

• Lecturer: Karima Galal Abdel Hameed, Professor of Milk Hygiene, Head of Food Hygiene Department, Faculty of Vet. Med., SVU
• Date: 21/14/2024
• Lecture type Lecture II

Microorganisms in Milk

• Classification: Microorganisms in milk are categorized as:
  • Non-pathogenic (desirable & spoilage)
  • Pathogenic (disease-producing bacteria)

Classification of Milk-Borne Illness

• Classification based on origin:
  • Disease of animal origin (Zoonotic)
  • Disease of human origin (Epidemic)
  • Disease of both animal & human origin
  • Disease of environmental origin
• Causative organisms:
  • Bacteria & Viruses
  • Fungi & Protozoa
  • Allergens & toxins

Milk-Borne Diseases Origin

• Animal & human origin: Zoonotic diseases (raw milk) & Epidemic disease (heat-treated milk) originate from animals and humans, respectively. Environmental origin occurs.
• Environmental origin: Diseases come from the environment.

Bacterial Diseases

• Bovine tuberculosis: Chronic infectious bacterial disease caused by Mycobacterium bovis from drinking infected raw milk. Gram-positive bacterium, acid-fast bacilli.
• Brucellosis: Chronic infection leading to recurrent/chronic fever in humans due to contaminated unpasteurized dairy products or contact with infected animals. Causative organism: Brucella.
• Leptospirosis: Sporadic bacterial disease with varying severity transmitted via contact with infected animal urine. Causative organism: Leptospira.
• Listeriosis: Bacterial disease characterized by monocytes in peripheral blood of immunocompromised patients and elders. Causative organism: Listeria monocytogenes.
• Pasteurellosis: Common wound infection following animal bites. Causative organism: Pasteurella multocida.
• Anthrax: Acute bacterial infection; can be fatal rapidly. Causative organism: Bacillus anthracis.
• Actinomycosis: Bacterial disease affecting submaxillary bone in humans, causing lumpy jaw, and affecting the udder in animals. Causative organism: Actinomyces bovis.

Viral Diseases

• Foot and Mouth Disease (FMD): Acute, highly infectious viral disease affecting cloven-footed animals (cows, buffaloes, sheep, goats). Causative organism: Foot and mouth disease virus (Picornaviridae).
• Rabies: Zoonotic, fatal viral disease affecting the central nervous system. Causative organism: Rabies virus.
• Cow pox: Viral infection between cattle and milkers via skin contact, during milking. Causative organism: Cow pox virus (Poxviridae).
• Tick-borne encephalitis: Viral disease affecting goats. Causative organism: Tick-borne encephalitis virus.
• Rift Valley fever (RVF): Viral zoonosis, affecting animals and humans, can cause severe disease and significant economic losses; sheep and goats are susceptible. Causative organism: RVF virus (Phlebovirus genus).

Protozoal Diseases

• Toxoplasmosis: Protozoal disease transmitted through ingestion of raw or improperly pasteurized milk containing trophozoites. Causative organism: Toxoplasma gondii trophozoite.
• Amoebiasis: Protozoal disease caused by ingestion of raw or improperly pasteurized milk containing cysts. Causative organism: Entamoeba histolytica cyst.

Rickettsial Disease

• Q fever (Coxiellosis): Acute febrile disease of humans caused by Coxiella burnetii. Dairy animals are a reservoir, ticks and insects can transmit the disease and milk can be a transmission vehicle.

Diagnosis, Prevention, and Control

• Many methods exist for diagnosing and controlling various diseases. These include testing for the causative organisms, treating affected animals, and controlling the environmental spread of the disease.

General Prevention and Control

• Heat treatment of milk to kill heat-sensitive organisms.