بسم الله الرحمن الرحيم Zoonoses Disease Lecture-1 Introduction

Definition Infection: pathogenic microorganisms penetrate the host defenses, enter the tissues, and multiply Disease: The pathologic state that results when something damages or disrupts tissues and organs Infectious disease: the disruption of a tissue or organ caused by microbes or their products -Pathogen: a microbe whose relationship with its host is parasitic and results in infection and disease Type and severity of infection depend on -Pathogenicity----of the organism and the condition of its host. (pathogenicity:the ability of an infectious agent to cause disease)

Emerging Infectious Disease An infectious disease that has newly appeared in a population or is rapidly increasing in incidence or geographic range On average, 1 newly identified infectious disease every year for each of the last 30 years (WHO)

Emerging Infectious Disease Approximately 75% of recent emerging infectious diseases have been zoonoses Avian Influenza Virus Ebola Virus Anthrax

DEFINITION Zoonoses : are infections which are naturally transmitted between vertebrate animals and people. The term zoonosis'Derived from the Greek ZOON (animals) and NOSES (diseases) People, animals, birds, arthropods and the inanimate environment are all involved in cycles of zoonotic infection

Reservoirs: Where Pathogens Persist Reservoir: the primary habitat in the natural world from which a pathogen originates Source: the individual or object from which an infection is actually acquired Living Reservoirs Carrier: an individual who inconspicuously shelters a pathogen and spreads it to others without any notice. Asymptomatic carriers Incubation carriers Convalescent carriers Chronic carrier Passive carrier

Animals as Reservoirs and Sources Vector: a live animal that transmits an infectious agent from one host to another Majority are arthropods Larger animals can also be vectors Biological vector: actively participates in a pathogen’s life cycle Mechanical vectors: transport the infectious agent without being infected

Figure 13.10

History

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Agent Environment Host Zoonotic diseases are multifactorial and their occurrence is affected by interactions between the host, the agent and the environment

Classification of zoonoses disease according to the mode of transmission Transmission of infections may be direct, indirect via arthropod vectors, or from environmental foci Direct zoonosis : the disease is directly transmitted from animals to humans through media such as air (influenza) or through bites and saliva (rabies). Cyclozoonosis :a zoonotic disease that requires at least two species of vertebrates as definitive and intermediate hosts. Examples: hydatid disease Metazoonosis:zoonoses require both a vertebrate host and an invertebrate host; an example is trypanosomiasis. Saprozoonosis Combination (e.g. direct & metazoonosis)

eg. histoplasmosis, Toxocara canis, certain food- borne diseases SAPROZOONOSIS Diseases of vertebrate animals which can affect people, the infectious agents of which are either capable of replicating in inanimate sites, or require an inanimate environment for the development of an infectious stage of their life cycle eg. histoplasmosis, Toxocara canis, certain food- borne diseases

Classification of zoonoses according the reservoir Anthropozoonoses: Zoonoses where the main reservoir of infection is non-human ,but vertebrate animals Most zoonoses are of this type e.g. bovine tuberculosis, rabies . Zooanthroponoses: Diseases that mainly affect people, which may be transmitted to animals, which then act as temporary reservoirs of infection Examples are Mycobacterium tuberculosis in dogs, infectious hepatitis in apes.

Zoonoses Classification : Animal Species Dogs & Cats as Rabies Roundworm Ringworm Cat Scratch Disease Food Animals Salmonella E.coli Brucellosis

Zoonoses: Animal Species Birds: Psittacosis West Nile virus Eastern Equine Encephalitis Avian Influenza Reptiles, Fish, & Amphibians Salmonella Mycobacterium Wild Animals Hantavirus Plague Tularemia Lyme Disease

Rabieses (viral infection) Rabies is a preventable viral disease of mammals most often transmitted through the bite of a rabid animal. The vast majority of rabies cases reported to the Centers for Disease Control and Prevention (CDC) each year occur in wild animals like raccoons, skunks, bats, and foxes. First recognized by Ancient Greeks, most historically known zoonosis. 97% rabies in US is because of dog bites, most occurs in South near Mexican border. 4.7 million people are bit by dogs each year, 386,000 require emergency treatment. Most common in Asia and Africa.

CLASSICAL RABIES(Direct zoonoses) Virulent rabies spread from Europe to Asia and other regions by infected dogs; many countries worldwide Dogs most important domestic hosts, cats, cattle and other domestic animals commonly involved Many wild reservoirs which differ between regions; principally canids (foxes, wolves, jackals) but also mongooses,,raccoons, bats Some countries free by eradication e.g. UK Direct zoonosis – bites, mucosal exposure, other routes e.g. corneal transplants Foxes, dogs, etc

Hanta virus First recognized in the Korean war in the 1950s along the Hantan river New strain causing Hantavirus cardiopulmonary syndrome recognized in America in 1993 Rodent reservoir www.kuleuven.be/ rega/mvr/research.html

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