Rodent-Borne Diseases
Rodents-Borne Diseases
•
Rodents are among the most abundant of wild
animal hosts of zoonoses
•
Diseases:
– Hantavirus infection
– leptospirosis
– bartonellosis
– Plague
Examples of Diseases Whose Health Impacts have been Influenced by Urbanization and Urban Poverty
• Hypertension
• Obesity
• Asthma
• Occupational diseases
• Violence
• Dengue
• Visceral leishmaniasis
• Tuberculosis
• Bacterial meningitis
• Acute rheumatic fever
Leptospirosis
•
Leptospirosis is a systemic disease of humans
and domestic animals, mainly dogs, cattle and
swine
•
Characterized by
– Fever
– renal and hepatic insufficiency,
– pulmonary manifestations
– reproductive failure
Global Burden and Epidemiology of
Leptospirosis
•
500,000 reported cases each year
(WHO. WeeklyEpid Rec. 1999;74:237-242)
•
Burden underestimated due to misdiagnosis
and lack of effective diagnostic tests
•
Traditionally, sporadic occupation-related
disease
Global Total Burden of Leptospirosis
•
Rural-based subsistence farming
– Wet-land farming (i.e. rice harvesting)
– Dry-land farming (i.e. sugar cane)
– Ubiquitous environmental exposures
•
The incidence is significantly higher in
Leptospirosis Causative Agent
• Spirochete
• Genus Leptospira (Adler et al, 2010)
– 13 pathogenic Leptospira species: L. alexanderi, L. alstonii
(genomospecies 1), L. borgpetersenii, L. inadai, L. interrogans, L. fainei, L. kirschneri, L. licerasiae, L. noguchi, L. santarosai, L.
terpstrae (genomospecies 3), L. weilii, L. Wolffii with > 260 serovars
– Saprophytic species of Leptospira include: L. biflexa, L. meyeri, L. yanagawae (genomospecies 5), L. kmetyi, L. vanthielii
(genomospecies 4), and L. wolbachii
> 60 serovars
• 6-20 µm x 0.1 µm
• Highly motile
– Periplasmic flagella
• Survives in environment weeks to months
Leptospira Classification
• Phenotypic/Serologic: (prior 1989)
– L. interroganspathogenic strains
– L. biflexasaprophytic strains
• Genotypic:
– L. borgpetersenii
– L. kirschneri
– L. weilii
– L. inadai
– L. parva
Leptospira
and Leptospirosis
• Tight, regular individual coils with a bend or hook at one or both ends
• L. biflexa – harmless, free-living saprobe
• L. interrogans – causes leptospirosis, a zoonosis
– bacteria shed in urine; infection occurs by contact with contaminated urine; targets kidneys, liver, brain, eyes
– sudden high fever, chills, headache, muscle aches, conjunctivitis, and vomiting
– Long term infections may affect kidneys and liver.
Transmission and Pathogenesis of
Leptospirosis
• The most widespread zoonosis
• Persistent colonization and shedding from renal tubules
• Transmission:
– Direct contact with reservoir
– Indirect contact with an environment contaminated with reservoir urine
– Animal bite rare
– Human-human ?? (sexual intercourse, breast feeding)
• Penetrate mucous membranes and breaks in skin
• Rapid dissemination and trophism to kidneys of reservoir hosts
Leptospirosis in Humans
• Incubation period: 2-30 days, usually 5-14 days
• Broad spectrum of manifestations
– Acute undifferentiated fever
– Influanza-like syndrome (fever, headache, myalgia)
– Aseptic meningitis (≤ 25% of all ases
– Weill’s disease jaundi e, renal failure, leeding,
myocarditis)
– Pulmonary hemorrhage respirtory failure
• Case fatality rate is 5-40%
– >50% for pulmonary hemorrhage syndrome
Leptospira Morbidity
•
This is not clear.
•
Leptospirosis may be underdiagnosed
because:
– The diagnosis is difficult to confirm;
– It may be confused with other diseases;
– The disease may be mild and not be investigated
in the laboratory.
Clinical Manifestation in Human
• Febrile illness
• Headache
• Myalgia
• Abdominal pain,
• conjunctival suffusion
• skin rash
• Cough
• Dyspnea
• hemoptysis
Differential Diagnosis
• Common viral infections, such as influenza
• Human immunodeficiency virus seroconversion
• Dengue
• Fever of unknown origin
• Typhoid.
• Encephalitis
• Poliomyelitis
• Rickettsiosis
• Glandular fever
(infectious mononucleosis),
• Brucellosis,
• Malaria,
Leptospirosis Treatment
•
Doxycycline (100 mg twice daily for 7 days)
•
Penicillin (amoxicillin, ampicillin)
•
Other choice: erythromycin, ceftriaxone and
cefotaxime
•
Prophylaxis:
CONTROL OF LEPTOSPIROSIS
•
At the source of infection
– Reservoir host
– Carrier
– Shedder
•
At the transmission route
•
At the level of the human host
Prevent Exposures to
Transmission Sources
• Disinfecting areas of
contaminated environment (hypochlorite)
• Protective clothing (boots, gloves)
• Cleaning wounds after exposure
• Prevention of contact with ill or dead animals
• Health education on risk exposures
• Remove transmission sources
• Inhibited at low detergent concentrations
Reservoirs
• Mice
– (Mus musculus and other Mus species)
• Rats
– mainly Rattus norvegicus and R. rattus
• Host-related serovars
– Mice
• Ballum
• Icterohaemorrhagiae
– Rats for Copenhageni
• Different rodent species may be reservoirs of distinct serovars.
• They usually do not show signs, but harbor leptospires in their kidneys, becoming an important source of infection
• Culturing of kidney tissues the most reliable method of detecting infection in animals.
• Rodent surveys require live-trapped animals
• Swine and cattle may be conducted at abattoirs after the animals are killed
• Culture of urine from live domestic animals
difficult and samples easily become contaminated.
Can the Environment be Checked for
Pathogenic Leptospires?
•
Detection
– Culture
• Samples of water and soil can be cultured and checked for growth of pathogenic leptospires Need long time
– PCR
– Animal Inoculation
•
Negative results
do not exclude the presence
Diagnosis of Leptospirosis
•
Specimens
– Blood in a heparin tube
– Cerebrospinal fluid
– Tissues microscopic examination and culture.
– Urine
– Serum for agglutination tests.
Methods for Diagnosis of Leptospirosis
•
Microscopic Examination
•
Culture
•
Serology (IgG/IgM/MAT)
Rickettsioses
• Acute febrile
• Zoonotic diseases caused by rickettsiae,
• Obligate intracellular Gram-negative bacteria
• Invade endothelial cells and induce the formation of vasculitis.
• Vectors: various arthropods, including lice, fleas, ticks, and mites,
• mammals and sometimes the arthropods them
Rickettsioses
• Diagnosis
– Culture
– PCR
– Serology (IFAT) – most aplicable
• Treatment
– Doxycycline
– Chloramphenicol
– Other macrolites
• Prevention
– Avoid exposure
– Repellent for the vectors
– No vaccination available
Plague
• Caused by the bacteria Yersinia pestis
• A zoonotic bacteria
• Usually found in small mammals and their fleas.
• It is transmitted between animals from their fleas.
• From 2010 to 2015 there were 3248 cases reported worldwide, including 584 deaths.
• Humans can be contaminated by
– the bite of infected fleas
– through direct contact with infected materials
•
Y pestis
exists as an obligate parasite and has a
limited ability to survive outside an infected
mammal
•
It is non
–
spore forming
•
Sensitive to sunlight and heating
•
Can not survive long in environment
plague
aerosol would be infectious for as long as 1
hour in a worst-case scenario
•
incubation period of one to seven days.
•
Case-fatality ratio of 30%-100% if left untreated.
•
Two main clinical forms of plague infection:
– Bubonic
• the most common form
• characterized by painful swollen lymph nodes or 'buboes'.
– Septicemic
Laboratory Diagnosis
•
Specimen: blood, aspirates from involved lymph
nodes, skin scrapings, cerebrospinal fluid, urine,
and sputum.
•
Y pestis identification :
– Bacteriologic : Microscopic and culture
– Serologic methods:
• Detection of capsular antigen F1 expressed only at 37°C
Hantavirus
• Bunyaviridae family
• May cause hantavirus pulmonary syndrome (HPS), a serious
respiratory disease.
• Hantavirus pulmonary syndrome
– respiratory distress
• pulmonary edema • cough
– fever
– myalgias
– nausea/vomiting
– elevated WBC, RBC
– T hrombocytopenia
– hypotension
• mortality = 50%
