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SALMONELLOSIS (Salmonella food poisoning, enteric paratyphosis) A common bacterial cause of food-poisoning worldwide. Over 1800 food-poisoning serotypes of salmonella ... – PowerPoint PPT presentation

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  • (Salmonella food poisoning, enteric paratyphosis)
    A common bacterial cause of food-poisoning
    worldwide. Over 1800 food-poisoning serotypes of
    salmonella (bacterium) exist.

  • (Hydrophobia, Lyssa) AGENT
  • - Rhabdovirus which causes an acute almost
    invariably fatal disease. RESERVOIR AND INCIDENCE
  • Worldwide distribution (

  • (Plague, Pest, black death, pestilential fever)
    During the course of the disease, 25,000,000
    people perished, a fourth of the population of
    the world. AGENT
  • a gram negative coccobacillus

  • Weil's disease, Hemorrhagic jaundice (Leptospira
    icterohaemorrhagiae), canicola fever (L.
    canicola), dairy worker fever (L. hardjo)
  • Spirochete, Leptospira. Pathogenic leptospires
    belong to the species Leptospira interrogans,
    which is subdivided into more than 200 serovars.
    The main natural reservoirs for human infection
    vary with serovar L. canicola in dogs, L. hardjo
    in cattle, L. pomona in swine, and L.
    icterohaemorrhagiae in rats.
  • Rats, mice, field moles, guinea pigs, gerbils,
    squirrels, rabbits, hamsters, reptiles, nonhuman
    primates, livestock, and dogs. In one study, 40
    of stray dogs were seropositive.
  • Handling affected animals, contaminating hands,
    or abrasions with urine, or aerosol

  • (Lyme arthritis, Bannworth's syndrome, tick-borne
    meningopolyneuritis, erythema chronicum migrans
    ECM, Steere's disease)
  • spirochete, Borrelia burgdorferi
  • First implicated in 1982 as agent in a 1975
    epidemic of juvenile inflammatory arthropathy in
    Old Lyme Connecticut. Cases have been reported
    from 46 states and the annual number of Lyme
    disease cases has increased 18 fold from 497 to
  • Transmitted mostly by Ixodes dammini and other
    ixodid ticks (three host tick with a two to three
    year life cycle). Ixodes dammini has a broad
    range of hosts adults prefer white tailed deer
    but will also parasitize dogs, horses, and
    humans. Larvae feed primarily on rodents,
    especially mice. Nymphs feed on all hosts and
    appears to be primarily responsible for
    transmission of the disease to people. Birds are
    an important reservoir and means of dispersal.
    Dogs appear to be at greater risk than humans.

  • (Relapsing fever, tick-borne relapsing fever,
    spirochetal fever, vagabond fever, famine fever)
    A widely distributed bacterial infection spread
    from wild rodents by ticks or lice, with high
    fatality Tick-borne relapsing fever occurs in
    Africa, the Americas, Asia and possibly parts of
  • The causative agents are Borrelia recurrentis and
    several other borrelia strains (bacterium).
  • Epidemic louse-borne infection is not considered
    zoonotic. Endemic tick-borne relapsing fever is
    transmitted from the natural wild rodent
    reservoir by tick bites to humans and dogs.
    Transovarial transmission in ticks occurs.
    Blood-borne person-to-person and intrauterine
    transmission have been reported.

  • (Vibriosis, vibrionic abortion)
  • Campylobacter (Vibrio) fetus ss. jejuni, a gram
    negative, microaerophilic, curved, motile rod
    that is worldwide in distribution.
  • Campylobacter species can be found in pet and
    laboratory animal species. Transmission
  • to humans is by the fecal-oral route and can
    produce an acute gastrointestinal illness.
    Symptoms include
  • diarrhea, abdominal pain, fever, nausea, and

  • (Pseudoglanders, Whitmore's disease)
  • Pseudomonas pseudomallei (Malleomyces
    pseudomallei, Actinobacillus pseudomallei )
    --MOTILE, Gram negative rod RESERVOIR AND
  • Normal inhabitant of surface soil and water in
    Southeast Asia, and tropical areas. Recent
    studies have shown that the water of tanks in
    which exotic aquarium fishes were imported was
    contaminated. Occurs in wild rodents, goats,
    pigs, sheep. Also identified in Chimps,
    orangutans, and macaques.
  • by inhalation from moist soil-water reservoir, by
    contact with contaminated soil or water thru
    overt or inapparent skin wounds, or by ingestion
    of contaminated feeds. Can be venereal in man.

  • (Francis' disease, deer-fly fever, rabbit fever,
    O'Hara disease) AGENT
  • - Francisella tularensis, a small pleomorphic,
    gram-negative, nonmotile rod or coccobacillus
    that can survive several weeks in the external
  • Common often fatal septicemic disease of rabbits,
    squirrels, muskrats, deer, bull snakes, sheep,
    wild rodents, cats and dogs. Major reservoirs are
    RABBITS, TICKS, MUSKRATS. Has been reported in
    NHP's at an urban zoo. Natural infection in
    laboratory animals and zoonotic transmission from
    them has NOT been reported.
  • handling tissue of infected animals (direct
    contact with UNBROKEN skin is sufficient).
    Reported human infections due to a cat bite and
    scratch and a NHP bite also reported. transmitted
    by biting insects inhalation, ingestion

  • (Streptobacillary fever, Haverhill fever,
    epidemic arthritic erythema, sodoku) AGENT
  • Gram negative, pleomorphic bacillus. Two
    different agents can cause disease 1.
    Streptobacillus moniliformis (Haverhill Fever)
    Named after a 1926 outbreak in Haverhill, Mass.
    attributed to contaminated milk. 2. Spirillum
    minus (Sodoku)
  • Present in the oral and respiratory passages of a
    large number of asymptomatic rodents, including
    Rats and Mice. Incidence of disease appears to be
    low. Historically, wild rat bites and subsequent
    illness (usually small children) relate to poor
    sanitation and overcrowding.
  • Man infected by bite of infected rodent or via
    contaminated milk or food

  • (Shipping or transport fever, hemorrhagic
    septicemia) AGENT
  • Pasteurella multocida, small, nonmotile,
    polymorphic, gram-positive bacilli RESERVOIR AND
  • inhabits the oral cavity and upper respiratory
    tract of many animals (Rabbits, rodents, dogs,
    cats, mice, birds, swine). Dogs and cats are
    frequently healthy carriers.
  • All animals and birds may be colonized by
    pasteurellas, and human infection occurs by wound
    infection from bites or scratches.
    Animal-to-animal transmission may occur by
    ingestion and inhalation. 1986 case report of
    meningitis in a woman who kissed her dog
    (cultured positive for organism) and also had
    dental caries which was considered to be the
    route of infection

  • (American Tick Typhus, Tick-borne Typhus Fever)
  • Rickettsia rickettsii.
  • Dogs, wild rodents and rabbits.
  • Ixodid ticks (especially Dermacentor) or their
    host species. Most rickettsias are obligate
    intracellular parasites of the gut cells of
    invertebrates and can only survive briefly
    outside living cells. Crushed ticks or mites and
    their feces may infect through broken skin.
    Transmission from tick bite occurs only after
    several hours of attachment.

  • (Vesicular Rickettsiosis, Kew Gardens Spotted
    Fever) AGENT
  • House mouse is reservoir host most commonly seen
    in rodent infested urban dwellings ie New York
    City and other Eastern U.S. cities. Rats and
    moles can also harbor the organism. Not
    identified as a natural disease in laboratory
  • Mite, Allodermanyssus sanguineus, transmits to
    mice or to man. Lab infections in humans via
    respiratory route have occurred but lab
    infections due to mite bite have not been reported

  • (Flea-borne Typhus Fever, Endemic Typhus Fever,
    Urban Typhus) AGENT
  • Rickettsia typhi RESERVOIR AND INCIDENCE
  • natural pathogen of rats and mice. Other mammals
    including cats, and their ectoparasites have been
    found infected. Outbreaks continue to occur in
    U.S., especially Texas. Natural lab infections
    have not been reported but lab acquired
    infections in people handling experimentally
    infected mice have been documented. TRANSMISSION
  • transmitted by flea or lice (Xenopsylla cheopis,
    Nosopsyllus fasciatus) to rodents or man. Humans
    are infected by contamination of flea bites,
    broken skin or conjunctiva by flea feces.
    Domestic animals may transport the flea vector to
    humans. Inhalation of contaminated dust may be a
    route of infection.

  • Venezuelan Equine Encephalitis
  • Arthropod borne ARBOVIRUSES
  • GENERAL In most man is an accidental host
    infected when arthropods feed on him. Therefore
    quarantine of wild caught animals and elimination
    of ectoparasites should prevent Examples TICK
    BORNE viruses 1. Russian-Spring-Summer
    Encephalitis 2. Louping Ill MOSQUITO BORNE
    viruses, ie 1. DENGUE (Breakbone Fever, Dengue
    Hemorrhagic Fever) AGENT Flavivirus,
    Flavidviridae RESERVOIR nonhuman primates,
    occurs in Asia, Africa, Australia, the Caribbean
    including Puerto Rico, the Pacific Islands, S.
    Europe, S. America TRANSMISSION mosquito vector
    (Aedes) DISEASE

Hantaviruses occur in rodent populations
world-wide. Rats and mice have been implicated in
outbreaks and infection of laboratory personnel
has resulted from infected rats. The virus
is shed in the respiratory secretions, saliva,
urine, and feces of infected animals and is
transmitted to humans On May 14, 1993, the New
Mexico Department of Health was notified of 2
persons who had died within 5 days of each other.
Their illnesses were characterized by abrupt
onset of fever, myalgia, headache, and cough,
followed by the rapid development of respiratory
failure. Tests for Yersinia pestis and other
bacterial and viral pathogens were negative.
After additional persons who had recently died
following a similar clinical course were reported
by the Indian Health Service, the health services
of Arizona, Colorado and Utah were contacted to
seek other possible cases. Blood and tissue
specimens were sent to the Centers for Disease
Control and Prevention (CDC). The results were
negative except for signals for the Puumala

  • The genus Hantavirus is a member of the family
    Bunyaviridae. Hantaviruses are further divided
    into genotypes. Representative viruses in each
    genotype are the Hantaan virus, the Seoul virus,
    the Puumala virus, and the Prospect Hill virus.
    Additional groups exist. Hantaan, Puumala, and
    Seoul viruses are known human pathogens Prospect
    Hill has not been associated with disease.
  • Rodents are the primary reservoir hosts with each
    hantavirus appearing to have a preferential
    rodent host. The epidemiological characteristics
    of outbreaks of human disease and the severity
    for the infection are determined mainly by the
    rodent host. Available data strongly supports the
    deer mouse (Peromyscus maniculatus) as the
    primary reservoir of the newly recognized
  • Infected rodents shed large quantities of virus
    in saliva, urine, and feces for many weeks, but
    the duration and period of maximum infectivity
    are unknown.

Lymphocytic Choriomeningitis Virus
  • Arenaviridae
  • Important zoonotic
  • agent
  • Wild mice principal
  • reservoir host
  • Laboratory mice hamsters
  • Horizontal transmission
  • Urine, saliva and milk
  • Vertical transmission

Lymphocytic Choriomeningitis Virus
  • Acquired perinatally
  • Persistent, asymptomatic, tolerant infection
  • Lifelong viremia and shedding
  • Disease
  • 7-10 months old
  • Emaciated
  • Rough hair coat
  • Hunched
  • Death

Lymphocytic Choriomeningitis Virus
  • Acquired after 1 week of life
  • Viremia, without virus shedding
  • Die acutely, or recover and eliminate virus
  • Adult mice
  • Subclinical

Lymphocytic Choriomeningitis Virus
  • Human
  • Clinical signs
  • Fever, headache, myalgia, nausea, vomiting, sore
    throat, photophobia
  • Differential diagnoses
  • Influenza, mononucleosis, herpes encephalitis,
    tuberculous meningitis

Lymphocytic Choriomeningitis Virus
  • Response to infection
  • Depopulate for public health considerations
  • Rederivation is not a viable option, due to in
    utero transmission

Sample Test Question
  • Which of the following rodent viruses can infect
    and cause flu-like symptoms in people? (Circle
    all correct answers)
  • Mouse hepatitis virus.
  • Rat coronavirus.
  • Lymphocytic choriomeningitis virus.
  • Ectromelia.
  • Enzootic diarrhea of infant mice.

Pneumonia Virus of Mice (PVM)
  • Paramyxoviridae
  • Infects mice, rats and hamsters
  • Natural infections are subclinical and
  • Immuno-compromised mice
  • Chronic pneumonia eventual death

  • Reoviridae
  • Uncommon in colonies today
  • Associated with clinical disease
  • Mouse
  • Group-A rotavirus
  • EDIM epizootic diarrhea of infant mice
  • Rat
  • Group-B rotavirus
  • IDIR infectious diarrhea of infant rats

  • Clinical signs
  • Neonatal diarrhea
  • Stunted growth, lethargy distended abdomens
  • Mortality low
  • Adults asymptomatic
  • Rat rotavirus may be zoonotic

Pneumocystis carinii
  • Protozoa vs. fungus
  • Ubiquitous, opportunistic microorganism
  • Life cycle within the lung alveoli
  • Latent infections in many species, including man
  • Different organism in rats and mice, than in
  • Normally nonpathogenic
  • Airborne transmission

Pneumocystis carinii
  • Clinical pneumonia is usually associated with
    pre-existing conditions
  • Neoplasia, immunodeficiency, immature immune
  • Treatment and Prophylaxis
  • Trimethoprim-sulfa
  • Albendazole
  • Control
  • Rederivation of infected colony

Pneumocystis carinii
Lungs Enlarged and solid Firm and rubbery
  • Organism clusters adhere to alveolar wall
  • Capillary blockage
  • Pulmonary insufficiency

Cryptosporidium muris
  • Protozoa, uncommon
  • Epithelial brush border
  • Mice - gastric colonization
  • Rats - Intestinal colonization
  • Zoonotic potential

Giardia muris
  • Protozoa - Lumen of anterior small intestine
  • Infects young and adult mice and rats
  • Low degree of pathogenicity, except in nudes
  • Rough hair coat, lethargy, distended abdomen
  • Diagnosis
  • Pear-shaped
  • trophozoites in SI
  • Cysts in feces

  • Common
  • Usually asymptomatic
  • Heavy infections associated with
  • Rectal prolapse, intussusception,
  • enteritis, fecal impaction
  • Can infect both mice and rats
  • Syphacia obvelata common mouse pinworm
  • Syphacia muris common rat pinworm
  • Aspicularis tetraptera

  • Syphacia spp.
  • Direct life cycle 11-15 days
  • Adults found in cecum and large intestine
  • Eggs deposited on perianal region
  • Infective 5-20 hours after release
  • Diagnosis
  • Cellophane tape test
  • Banana shape
  • Fecal exam is NOT reliable

  • Aspicularis tetraptera
  • Direct life cycle 23-25 days
  • Adults found in large intestine, not cecum
  • Eggs passed in feces
  • Infective 5-8 days after excretion
  • Diagnosis
  • Fecal examination
  • Football shape
  • Cellophane tape test - NOT reliable

  • Treatment Anthelmintics
  • Ivermectin
  • Injection, micro-dot, misting, drinking water
  • Sensitive mouse strains, eg. C57Bl/6
  • Fenbendazole
  • Feed or drinking water
  • Multiple treatments
  • Control
  • Rederivation, depopulation, isolation, strict

  • Hymenolepis nana Dwarf tapeworm
  • Direct or indirect life cycle
  • Clinical signs heavy infection
  • Retarded growth, weight loss, intestinal
  • Small intestine
  • Zoonotic potential

  • Hymenolepis diminuta
  • Indirect life cycle
  • Arthropod intermediate host
  • Clinical signs
  • Similar to H. nana
  • Upper small intestine
  • Zoonotic potential

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Pediculosis louse infestation
  • Polyplax serrata (mice)
  • Polyplax spinulosa (rats)
  • Sucking lice
  • Direct contact transmission
  • Adults - host anterior dorsum
  • of host
  • Eggs attach are base of hair
  • Clinical signs
  • Anemia, unthriftiness, debilitation
  • Vector of disease transmission
  • Examples hemobartonella, tularemia,
    trypanosomes, rickettsia

  • Dental formula I 1/1 C 0/0 P 0/0 M 3/3
  • Incisors grow continuously throughout life span

Mammary Tumors
  • Common in aged mice and rats
  • Can grow rapidly
  • Rats
  • Benign fibroadenoma
  • Mice
  • Malignant adenocarcinoma

Miscellaneous Alopecias
  • Bite wounds
  • Male mice fight viciously
  • Barbering
  • Dominance behavior
  • Shaved, nonerythematous appearance
  • C57Bl/6 necrotizing dermatitis

  • Mycoplasma pulmonis
  • Small, gram-negative, pleomorphic organism
  • Lacks a cell wall
  • Mice and rats are natural hosts
  • Vertical and horizontal transmission
  • Clinical signs
  • Often subclinical
  • Upper respiratory
  • snuffling, chattering
  • oculonasal discharge
  • Sick rodent signs

  • Pathology
  • Colonizes luminal surface of respiratory
  • Purulent rhinitis, otitis media, tracheitis,
    bronchitis, bronchopneumonia
  • Rat marked hyperplasia of bronchus associated
    lymphoid tissue (BALT)
  • Also other tissues, such as female genital tract
  • Endometritis, pyometra, salpingitis,

  • Control
  • Treatment with antibiotics (tetracycline)
    suppress overt disease, but is not curative
  • Rederivation may not be successful due to in
    utero transmission
  • Procure mycoplasma-free animals
  • Rigid sanitation

  • S. typhimurium, S. enteritidis
  • Fecal-oral transmission
  • Clinical signs
  • Sick rodent signs, diarrhea
  • Pathology
  • Splenomegaly
  • Multifocal hepatic necrosis
  • Control
  • Prevent wild rodent
  • contamination

Tyzzers Disease
  • Clostridium piliforme
  • (Bacillus piliformis)
  • Gram-negative, spore-former
  • Hosts mice, rats, other rodents,
  • rabbits, horses, dogs
  • Fecal-oral transmission
  • Clinical signs
  • Most often in weanlings
  • Mice diarrhea, body wasting
  • sudden death
  • Rats abdominal distention
  • diarrhea is uncommon
  • Morbidity and mortality varies

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AAALAC Association for Assessment and
Accreditation of Laboratory Animal Care
International AALAS American Association for
Laboratory Animal Science AC Animal Care, APHIS,
USDA ACLAM American College of Laboratory Animal
Medicine AGRICOLA National Agricultural
Librarys Agricultural OnLine Access (USDA)
APHIS Animal and Plant Health Inspection Service
(USDA) ARENA Applied Research Ethics National
Association ASLAP American Society of Laboratory
Animal Practitioners AV Attending Veterinarian
AVMA American Veterinary Medical Association
AWA Animal Welfare Act AWIC Animal Welfare
Information Center AWRs Animal Welfare
Regulations (USDA)
  • Arenavirus Of many latent viruses present in
    mice, only LCM naturally infects humans. LCM can
    easily be transmitted from animals to humans.
    Isolated by Armstrong and Lillie during
    investigation of a St. Louis Encephalitis
    outbreak in 1933. RESERVOIR AND INCIDENCE
  • Worldwide in wild mice (M. musculus). This
    disease is principally confined to the eastern
    seaboard and northeastern states in the U.S. Wild
    mice infect the lab mouse. Mouse and hamster are
    the only species in which long term, asymptomatic
    infection is known to exist. LCM virus is
    present in experimental mouse tumors which is a
    second source of infection for humans. This was
    first recognized in a transplantable leukemia of
    C58 mice. The disease can also be transmitted to
    laboratory animals via inoculation of infected
    tissue culture cells. The infection also occurs
    in guinea pigs, rabbits, rats, canines, swine,
    and primates. TRANSMISSION
  • Infection in mice is maintained by congenital
    infection followed by lifelong carriage and
    excretion of virus in saliva, urine, and feces.
    Human infections are probably from contaminated
    food and dust, the handling of dead mice, and
    mouse bites. Bloodsucking arthropod vectors such
    as ticks, lice, and mosquitos may transmit the
    disease. Person to person transmission does not

  • (Piroplasmosis) AGENT
  • Babesiosis in humans is a rare intraerythrocytic
    infection caused by Babesia divergens and
  • Natural hosts for B. microti are various wild and
    domestic animals, particularly the white-footed
    mouse and white-tailed deer. With extensions of
    the deer's habitat, the range of human infection
    appears to be increasing. In the USA, the
    parasite has been found in coastal and island
    areas of the northeast and mid-Atlantic states as
    well as Wisconsin, Minnesota, and California. B.
    divergens occurs in Europe. TRANSMISSION
  • Humans are infected as a result of Ixodes tick
    bites, but transmission from blood transfusion
    has also been reported. Splenectomized, elderly,
    or immunosuppressed persons are the most likely
    to have severe manifestations.

  • (Chagas's Disease, Chagas-Mazza Disease, South
    American Trypanosomiasis) AGENT
  • Trypanosoma cruzi RESERVOIR AND INCIDENCE
  • Dogs, cats, and guinea pigs are the main
    reservoirs for human infection. T. cruzi occurs
    only in the Americas it is found from southern
    South America to northern Mexico, Texas, and the
    southwestern U.S. An estimated 12 million people
    are infected, mostly in rural areas, resulting in
    about 60,000 deaths yearly. TRANSMISSION
  • Humans are infected when the insect's feces
    become rubbed into the wound caused by the bite
    of an infected bloodsucking insect (triatomid) or
    when the conjunctiva, mucous membranes or
    abrasions become contaminated. After invading
    local reticuloendothelial cells, the trypanosome
    multiplies in the blood. Adaption of triatomid
    vector to the human domestic environment allows
    transfer of infection between animals, from
    animals to humans or from human to human.
    Transmission by blood transfusions from infected
    persons, congenital infection, breast milk and
    laboratory accidents are possible.

  • Cutaneous leishmaniasis Chiclero ulcer,
    espundia, pianbols, uta, and buba (in the
    Americas) oriental sore, Aleppo boil (in the Old
    World) Bagdad boil, Delhi boil, Bauru ulcer (in
    the Middle East). Visceral leishmaniasis
    kala-azar AGENT
  • The causative agents of cutaneous leishmaniasis
    are Leishmania mexicana and L. brasiliensis in
    the Americas, and L. tropica in the Old World
    and of visceral leishmaniasis, L. donovani, L.
    infantum, and L. chagasi. RESERVOIRS AND
  • The geographic distribution of the cutaneous
    disease is Texas, Mexico, Central and South
    America, India, Pakistan, the Middle East,
    southern Russia, the Mediterranean coast and
    Africa. The distribution of visceral
    leishmaniasis is poorly reported, but foci
    probably occur in the Mediterranean basin, the
    Middle East, India, China, Mexico, Central and
    South America, and Africa. Wild animals, dogs and
    humans serve as reservoirs. Domestic dogs may be
    an important reservoir for humans. Humans are the
    only known reservoir in India. TRANSMISSION
  • Sandfly vectors transmit cutaneous leishmaniasis.
    Person-to-person, congenital, and blood-borne
    transmission of visceral leishmaniasis are

  • The causative agents are Capillaria hepatica
    (hepatic form), C. philippinensis (intestinal
    form) and C. aerophila (respiratory form).
  • C. hepatica and C. aerophila are very rare
    infections with isolated cases reported from
    North, Central and South America, Asia, and
    Europe. C. philippinensis is endemic in certain
    areas of the Philippines and cases have been
    reported from Thailand and Japan. Humans are the
    reservoir for C. philippinensis. With C.
    hepatica, rodents are the reservoirs. Cats and
    dogs are the reservoir for C. aerophila.
    Peromyscus maniculatus and Cletheronomys gapperi
    are the major hosts in North America.
  • Humans are infected by eating raw fish containing
    infective larvae. The worm parasite lives in the
    intestines of humans and autoinfection occurs.
    Human feces contain large numbers of ova which
    contaminate watercourses and infect freshwater
    fish. Humans may be infected by the ingestion of
    ova in the soil also.

  • Trichinella spiralis, an intestinal nematode.
  • Swine, dogs, cats, rats and many wild animals.
    Worldwide. In the U.S., there has been a marked
    reduction in the prevalence of trichinosis both
    in humans and pigs prevalence in commercial pork
    now ranges from nil to 0.7. Fewer than 100 human
    cases are reported annually and usually have been
    as a result of eating homemade sausage and other
    meat products using pork, horse meat, or arctic
    mammals. TRANSMISSION
  • In the natural cycle, larvae develop into adult
    worms in the intestines when a carnivore ingests
    parasitized muscle. Pigs generally become
    infected by feeding on uncooked scraps or, less
    often, by eating infected rats. In humans,
    infection occurs by eating insufficiently cooked
    meat. In the epithelium of the small intestine,
    larvae develop into adults. Gravid female worms
    then produce larvae, which penetrate the
    lymphatics or venules and are disseminated via
    the bloodstream throughout the body. The larvae
    become encapsulated in skeletal muscle.

  • Angiostrongylosis, eosinophilic meningitis or
    meningoencephalitis (A. cantonensis), abdominal
    angiostrongylosis (A. costaricensis). ETIOLOGY
  • Two metastrongylids, Angiostrongylus
    (Morerastrongylus) costaricensis and A.
    cantonensis, are the etiologic agents. The first
    species is responsible for abdominal
    angiostrongyliasis, and the second one for
    eosinophilic meningitis or meningoencephalitis.The
    definitive hosts of both species are rodents
    man is an accidental host. Both species require
    mollusks as intermediate hosts for the completion
    of their life cycle. The main definitive host of
    A. costaricensis is the cotton rat, Sigmondon
    hispidus, in which the adult nematode lodges in
    the mesenteric arteries and their branches on the
    intestinal wall. The first-stage larva emerges
    from eggs laid in the arteries, penetrates the
    intestinal wall, and is then carried with the
    fecal matter to the exterior. In order to
    continue their development, the first-stage
    larvae have to be ingested by a slug. Vaginulus
    ameghini, in which they change successively into
    second- and third-stage larvae. When the
    infective third-stage larva is ingested by a
    rodent, it seeks the ileocecal region, where it
    penetrates the intestinal wall and locates in the
    lymphatic vessels (both inside and outside the
    abdominal lymph nodes). In this location the
    larvae undergo two molts before migrating to
    their final habitat, the mesenteric arteries of
    the cecal region. Oviposition begins after about
    18 days. and the first-stage larvae appear in the
    feces 24 days after infection (prepatent period).
    In man, an accidental host. the parasite can
    reach sexual maturity and produce eggs, but the
    eggs usually degenerate, causing a granulomatous
    tissue reaction.

  • The development cycle of A. cantonensis is
    similar to that of A. costaricensis. The
    intermediate hosts are various species of land
    snails, slugs, and freshwater snails. The
    definitive hosts can become infected by ingesting
    infected snails, or plants and water contaminated
    by them with the third larvae. In addition,
    infection can occur as a result of consuming
    transfer hosts (paratenic hosts), such as
    crustaceans, fish, amphibians, and reptiles,
    which in turn have eaten infected mollusks
    (primary intermediate hosts). The definitive
    hosts of A. cantonensis are primarily various
    species of the genus Rattus. When they enter a
    rat's body, the third-stage larvae (which
    developed in a mollusk) penetrate the intestine
    and are carried by the circulatory system to the
    brain, where they undergo two more molts and
    become young adult parasites. From the cerebral
    parenchyma they migrate to the surface of the
    brain. They remain for a time in the subarachnoid
    space and later migrate to the pulmonary
    arteries, where they reach sexual maturity and
    begin oviposition. The eggs hatch in the
    pulmonary arterioles, releasing the first larva,
    which migrates up the trachea, is swallowed, and
    is eliminated with the feces. Mollusks are
    infected by ingesting fecal matter of infected
    rodents. In man, who is an accidental host, the
    larvae and young adults of A. cantonensis
    generally die in the brain, meninges, or medulla
    oblongata. The nematode can occasionally be found
    in the lungs.

  • Abdominal angiostrongyliasis, caused by A.
    costaricensis, is a parasitosis described a few
    years ago in Costa Rica it is one of the most
    recently recognized zoonoses. Human disease has
    also been confirmed in Honduras, El Salvador, and
    Brazil. Suspected clinical cases have occurred in
    Nicaragua and Venezuela. In Panama, the adult
    parasite was found in five species of rodents
    belonging to three different families. In the
    past few years, the parasite has been found in
    several specimens of Sigmodon hispidus in Texas,
    USA. Ozyomys caliginosus in Colombia and slugs
    in Guayaquil, Ecuador. The parasitosis is
    probably much more widespread than is currently
    recognized. A. costaricensis has not been
    recorded outside the Americas. Human cases of
    parasitism by A. cantonensis have occurred in
    Thailand, Vietnam, Kampuchea, the Philippines,
    Indonesia, Taiwan, Japan, Australia, and several
    Pacific islands. The parasite is much more widely
    distributed, and its existence in rats has been
    confirmed in southern China, India, Malaysia, Sri
    Lanka, Madagascar, Mauritius, and Egypt. Until
    recently, the geographic distribution of A.
    cantonensis was thought to be limited to Asia,
    Australia, the Pacific islands, and Africa.
    However, in recent years its presence has been
    confirmed in Cuba, where infected rats (Rattus
    norvegicus) and mollusks have been found
    likewise, five human cases of meningoencephalitis
    have been attributed to A. cantonensis in that
    country. It is believed that the parasite was
    introduced to the island some years ago by rats
    from a ship from Asia. In a study carried out on
    rat species (R. norvegicus, R. rattus, and R.
    exulans) on the Hawaiian and Society Islands, the
    parasite was found in more than 40 of the
    specimens captured. In Egypt, 32.7 of 55
    specimens of R. norvegicus harbored the parasite.
    In the province of Havana, Cuba, 12 out of 30
    captured R. norvegicus were infected. In view of
    the worldwide distribution of R. norvegicus and
    R. rattus, these rodents were examined for the
    parasite in Puerto Rico, London, and New Orleans,
    but the results were negative. Eosinophilic
    meningitis associated with infection by A.
    cantonensis has been recorded in several hundred
    patients in endemic areas.

  • Dwarf tapeworm, Hymenolepis nana - measures 5-90
  • The animal reservoir is the house mouse, but
    humans can be both definitive and intermediate
    hosts. Worldwide occurrence in warm climates.
  • Gravid proglottids disintegrate and eggs pass in
    the feces and may be ingested by another human.
    Larvae then develop in the intestinal villi and
    pass to the lumen of the gut to become the adult
    forms. Dogs, cats and their fleas can be infected
    as well as grain beetles which can serve as
    intermediate hosts.

  • Larval diphyllobothriasis. ETIOLOGY
  • The second larval stage (plerocercoid or
    sparganum) of the pseudophyllidean cestode of the
    genus Spirometra (Diphyllobothrium, Lueheela).
    Several species of medical interest have been
    described Spirometra mansoni, S. mansonoides, S.
    erinacei-europaei, S. theileri, and S.
    proliferum. These are the most commonly accepted
    species at the present time, but it should be
    noted that they are difficult to differentiate
    and that the taxonomy remains in doubt. The
    definitive hosts are mainly domestic and wild
    canids and felids. The development cycle requires
    two intermediate hosts. The first is a copepod
    (planktonic crustacean) of the genus Cyclops.
    which ingests coracidia (free, ciliated embryos)
    that develop from Spirometra eggs when they reach
    the water with the feces of dogs or cats
    (definitive hosts). In the tissues of the
    copepod, the coracidium turns into the first
    larva, or procercoid. When a second intermediate
    host ingests an infected copepod, the procercoid
    develops into a second larval form, the
    plerocercoid or sparganum. The plerocercoid larva
    can be harbored by many vertebrates, including
    amphibians, reptiles, birds, small mammals
    (rodents and insectivores), man, nonhuman
    primates, and swine. Fish do not become infected.
    Some researchers believe that the second
    intermediate host is usually an amphibian, but
    can vary according to region. Numerous species of
    vertebrates become infected with plerocercoids by
    feeding on amphibians, but they may also develop
    plerocercoids after ingesting water containing
    copepods infected by procercoids (first larva).
    Several animal species that are not definitive
    hosts function as paratenic or transport hosts,
    since the larvae they acquire by feeding on
    animals infected with plerocercoids encyst again
    after passing through the intestinal wall and
    migrating to other tissues. This transfer process
    is undoubtedly important in the life cycle but
    the fact that many species of secondary hosts can
    be infected directly by ingestion of copepods
    containing procercoids is probably no less
    important. When the sparganum reaches the
    intestine of the definitive host, it attaches to
    the mucosa in 10 to 30 days, it matures into an
    adult cestode, completing the cycle. The adult S.
    mansonoides reaches about 25 cm in length in the
    intestine of the definitive hosts (cat, dog). The
    sparganum found in the tissues of the secondary
    intermediate hosts and paratenic hosts, including
    man, varies from 4 to 10 cm in length.

  • (Bilharzia, Bilharziasis) AGENT
  • Schistosomiasis infects more than 200 million
    persons worldwide. The causative agents are
    Schistosoma mansoni, haematobium, and japonicum.
  • Humans are the reservoir for S. mansoni and
    haematobium. S. japonicum infects cattle, water
    buffalo, horses, dogs, cats, rodents and monkeys.
    Intermediate hosts are species of snails
    (Biomphalaria and Bulinus). S. mansoni occurs in
    Africa, South America and some Caribbean islands
    (including Puerto Rico) S. haematobium in Africa
    and the Middle East and S. japonicum in China,
    Japan, the Philippines, and South East Asia.
  • Cercariae in contaminated water penetrate human
    skin, especially in irrigated fields or rivers.
    In the body the parasite migrates via the liver
    to the superior mesenteric vein where maturation
    takes place in about 6 weeks. Eggs are
    disseminated throughout the body via the blood,
    released into the intestinal lumen and excreted.
    In water miracidia develop and penetrate the
    snail, which in turn excretes cercariae into the