chapter 81 - Zoonotic infections.pptx

Learning objectives
2
At the end of the session, the students will be able to understand:
▰ Common zoonotic infections
▰ Epidemiology, virulence factors, clinical types, lab diagnosis, treatment and
prevention of plaque and tularemia.
▰ Bite wound infections and agents causing the infections

INTRODUCTION
3
▰ Zoonosis is any disease or infection that is naturally transmissible from
vertebrate animals to humans.
▰ Animals thus play an essential role in maintaining zoonotic infections in
nature.
▰ Zoonoses - associated with bacterial, viral, or parasitic, or due to fungal
agents .

Important zoonotic infections affecting human
beings and their usual sources
4
Essentials of Medical Microbiology
Bacteria Animals
Anthrax Herbivores
Plague Rat
Brucellosis Sheep, goat, camel
Pasteurella infection Dog, cat
Capnocytophaga infection Dog
Rat bite fever Rodents
Leptospirosis Rodents
Non-typhoidal salmonellosis Poultry
Bovine tuberculosis Cow
Endemic typhus Rodents
Tularaemia Rabbits
Viruses Animals
Rabies Dogs
Yellow fever Monkeys
Japanese B encephalitis Pigs
Kyasanur forest disease Monkeys
Chikungunya Monkeys
Monkey pox Monkeys
Prion diseases Cattle
Hemorrhagic fevers Rodents, cattle, wild animals
Influenza Pigs, birds

beings and their usual sources (Cont..)
5
Fungi Animals
Zoophilic dermatophytoses
Trichophyton equinum Horse
Trichophyton simii Dogs, poultry
Microsporum canis Dogs
Microsporum equinum Horse
Sporothrix Cats
Malassezia Dogs, cats
Cryptococcus Wide variety of
animals, birds
Penicillium marneffei Bamboo rats
Lacazia loboi Dolphins
Conidiobolus Horses
Fungi Animals
Histoplasma Cattle, sheep
Coccidioides Dogs
Paracoccidioides Dogs
Blastomyces Dogs
Pneumocystis jirovecii Rodents

beings and their usual sources (Cont..)
6
Parasites Animals
Toxoplasma Cats
Leishmania Dogs
Taenia Pigs, cattle
Echinococcus Dog
Cryptosporidium Cattle
Fasciolopsis buski Pigs, cattle
Trichinella Pigs
Hookworms and Roundworms Dogs and cats
Dirofilaria and zoonotic
Brugia species
Dogs, cats, raccoons, etc.

Classification
7
▰ Anthropozoonoses: Infections transmitted from animals to man
▰ Zooanthroponoses: Infections that are transmitted from man to animals
▰ Amphixenoses: Infections that are maintained in both man and animals that
may be transmitted in either direction.

COMMON ZOONOTIC
INFECTIONS 8

PLAGUE (YERSINIA
PESTIS) 9

PLAGUE (YERSINIA PESTIS)
10
▰ Tribe Yersinieae - genus Yersinia - three well-established human pathogens
 Yersinia pestis: rodent-borne zoonotic disease – plague
 Yersinia pseudotuberculosis and Y.Enterocolitica— cause yersiniosis, a
self-limiting gastrointestinal illness

Plague Pandemics
11
▰ First pandemic (in AD 541): Caused by biotype ‘Medievalis’
▰ Second pandemic (in 14th century) was called black death, Caused by biotype
‘Antiqua’
▰ Third pandemic (1894): Mainly affected India and China. Caused by biotype
‘Orientalis’.

Timeline of Plague in India
12
▰ 1896 to 1918: Hong Kong pandemic entered India and millions of people were
killed
▰ 1918 to 1967: gradually declined, sporadic cases continued in endemic foci
▰ 1967 to 1994: No plague cases were reported

Timeline of Plague in India (Cont..)
13
▰ 1994 (Surat epidemic): It started as bubonic plague from Beed-Latur belt in
Maharashtra - pneumonic plague - spread to Surat and adjoining regions of
Gujarat - 60 deaths in two months
▰ 2002 (Shimla outbreak): A short outbreak at Rohru, near Shimla. Four deaths
▰ 2004 (Uttarkashi outbreak): Localized outbreak of bubonic plague (8 cases
and 3 deaths) - Dangud village of Uttarkashi district, Uttaranchal

Timeline of Plague in India (Cont..)
14
▰ Four potential endemic foci
1. Region near Kolar, Karnataka
2. Beed-Latur belt in Maharashtra
3. Rohru in Himachal Pradesh
4. Dangud village, Uttaranchal

Epidemiological Factors
15
▰ Reservoir: Wild rodents, field mice & bandicoot
▰ Source of infection - wild rodents, rat fleas, cases of pneumonic plague
▰ Vector: Rat flea
 Xenopsylla cheopis - Most efficient, North India
 Xenopsylla astia - Less efficient, South India
 Xenopsylla brasiliensis

Epidemiological Factors (Cont..)
16
▰ Mode of transmission:
 Bite of an infected rat flea (most common)
 Direct contact with tissues of infected animal (rodents)
 Droplet inhalation (man to man) - pneumonic plague
 Bite of an infected human flea (Pulex irritans)

17
Blocked flea:
 Bacilli multiply enormously in the gut of flea and may block the proventriculus
- while making efforts to suck, it regurgitates the blood mixed bacteria into the
bite - transmission of infection
 Contamination of bite wound with feces of infected fleas
 Partially blocked flea is more dangerous than a completely blocked flea

18
▰ Extrinsic incubation period – two weeks for Xenopsylla cheopis
▰ Cheopis index - Average number of X.cheopis per rat is most significant flea
index
 Cheopis index >1  outbreak likely
▰ Seasonality: North India - September to May, South India - throughout the year

Virulence Factors of Y. pestis
19
Fraction 1 (F1) antigen:
▰ Capsular protein antigen, encoded by a plasmid (pFra).
▰ Acts by inhibiting phagocytosis by macrophage.
▰ Highly antigenic and is used as immunodiagnostic marker of infection

Virulence Factors of Y. pestis (Cont..)
20
▰ Other virulence factors include—Phospholipase D (murine toxin), surface
proteases, pH 6 antigen, lipopolysaccharide (endotoxin), pigments (hemin-
containing), type III secretion system, adhesins (help in attachment), and
siderophore (helps in acquisition of iron)

Human Plague: Clinical Types
21
▰ Bubonic
▰ Pneumonic
▰ Septicemic

Bubonic Plague
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▰ Most common type, transmitted by the bite of an infected rat flea
▰ Bacilli pass through the local lymphatics - regional lymph nodes - multiply
▰ Incubation period: 2–7 days
▰ Sudden onset, fever, malaise, headache & painful lymphadenitis
▰ Cannot spread from person to person

Bubonic Plague (Cont..)
23
▰ Buboes: Regional lymph nodes - tense,
tender swellings “buboes”
 Common site - inguinal
 Other sites - crural, axillary, cervical, or
submaxillary

Pneumonic Plague
24
▰ Spread: Inhalation of bacilli in droplets expelled from another person or an
animal with plague pneumonia
▰ Incubation period: 1–3 days
▰ Manifestation: Sudden onset fever, headache and respiratory symptoms pain ™
▰ Rare (<1%) but highly infectious and highly fatal
▰ Agent of bioterrorism

Septicemic Plague
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▰ Secondary septicemic plague is more
common than Primary
▰ From spread of bubonic or pneumonic plague
▰ Incubation period:2–7 days
▰ Hemorrhages in the skin and mucosa -
gangrene of affected site - black death

Laboratory Diagnosis - Specimen Collection
26
▰ Bubonic plague—pus or fluid aspirated from buboes
▰ Pneumonic plague—sputum and blood
▰ Septicemic plague—blood and splenic aspirate (post mortem)
▰ Transport medium - Cary–Blair medium

Laboratory Diagnosis - Direct Microscopy
27
▰ Gram staining: Gram negative oval
coccobacilli surrounded by
capsule
▰ Wayson stain or methylene blue
stain - bipolar or safety pin
appearance

Laboratory Diagnosis - Culture
28
▰ Y. pestis is aerobic and facultatively anaerobic
▰ Blood agar: Non-hemolytic and dark brown pigmented colonies (absorption of
the hemin)
▰ MacConkey agar: Lactose non-fermenting

Laboratory Diagnosis - Culture Smear and
Motility Testing
29
▰ Gram staining of culture smear - pleomorphism-coccid, coccobacillary,
bacillary, filamentous and giant forms.
▰ Y. pestis - nonmotile both at 25°C and 37°C; in contrast to other Yersinia
species which are motile at 25°C and nonmotile at 37°C.

Laboratory Diagnosis - Identification
30
▰ Catalase positive and oxidase negative
▰ ICUT tests: Indole test (negative), citrate test (negative), urease test (negative)
and TSI (triple sugar iron agar) test shows alkaline/acid, gas absent, H2S
absent
▰ MALDI-TOF - rapid accurate identification of Y. pestis and also to differentiate
its three biotypes.

Laboratory Diagnosis - F1 Antigen Detection
31
▰ From bubo aspirate or sputum by direct immunofluorescence test, ELISA or
immunochromatographic test (ICT)

Laboratory Diagnosis - Antibodies to F1 Antigen
Detection
32
▰ By ELISA, passive agglutination or CFT
▰ Limited diagnostic value as they appear late
▰ Useful epidemiological markers

Laboratory Diagnosis - Molecular Methods
33
▰ PCR – gene coding F1 antigen, pesticin gene, and the plasminogen activator
gene

Treatment of Plague
34
▰ Streptomycin - treatment for plague in the past, given for 10 days
▰ Gentamicin is superior to streptomycin and currently recommended for
treatment
▰ Levofloxacin - recently been approved for treatment and for post-exposure
prophylaxis

Treatment of Plague (Cont..)
35
▰ Alternative drugs - doxycycline and chloramphenicol are also effective.
▰ β-lactams and macrolides - not recommended as the response is poor.

Prevention of Plague
36
▰ Control of cases by early diagnosis, isolation and treatment of cases
▰ Control of fleas by use of effective insecticides - DDT or BHC
▰ Control of rodents
▰ Chemoprophylaxis - all contacts of pneumonic plague - Doxycycline or
levofloxacin - for 7 days

Prevention of Plague (Cont..)
37
Vaccine: For prevention of an anticipated outbreak and not for general use
▰ Formalin killed vaccine (Sokhey’s modification of original Haffkine vaccine):
 Subcutaneous, two doses 4 weeks apart - booster after 6 months
 Protection is short-lasting (<6 months)
 Not protective against pneumonic plague and has considerable side effects

Prevention of Plague (Cont..)
38
Vaccine (Cont..):
▰ Live attenuated vaccine based on strain EV76
 Still used in countries of the former Soviet Union
 Has significant side effects

TULARAEMIA (FRANCISELLA
TULARENSIS)
39

TULARAEMIA (FRANCISELLA TULARENSIS)
40
▰ Causative agent of ‘tularemia’ primarily a plague-like disease of rodents and
other small animals
▰ Human infection is zoonotic and usually results from:
 Interaction with biting or blood-sucking insects (especially ticks and
tabanid flies)
 Ingestion of contaminated water or food
 Inhalation of infective aerosols.

Prevalence
41
▰ Four subspecies: tularensis, holarctica, novicida, and mediasiatica
▰ First three subspecies are found in North America, whereas subspecies
mediasiatica is found in centralAsia
▰ Subspecies tularensis - most common & most virulent among all.

Clinical Manifestations
42
▰ Ulceroglandular tularemia: Ulcerative lesion at the site of inoculation, with
regional lymphadenopathy
▰ Other forms include—Pulmonary, oropharyngeal, oculoglandular form and
typhoid-like illness

Clinical Manifestations (Cont..)
43
▰ Complications: Suppurated lymph nodes, acute kidney injury, hepatitis,
rhabdomyolysis, empyema, pericarditis, meningitis, osteomyelitis and
endocarditis
▰ Agent of bioterrorism

Laboratory Diagnosis
44
▰ Culture: Highly fastidious - special media - BCG agar (blood cysteine glucose
agar)
▰ Specimen: Ulcer scrapings, and lymph node biopsy are the preferred
specimens
▰ Safety precautions - biosafety level III must be used to handle clinical
specimens to avoid the risk of laboratory-acquired infection

Laboratory Diagnosis (Cont..)
45
▰ Antibody detection - Agglutination tests (latex and tube agglutination) and
ELISA
▰ PCR assay - F. tularensis specific genes encoding the outer-membrane
proteins - also differentiate subspecies.

Treatment of Tularemia
46
▰ Gentamicin - drug of choice; given for 7–10 days.
▰ Doxycycline or ciprofloxacin - alternatives.

BITE WOUND
INFECTIONS 47

BITE WOUND INFECTIONS
48
▰ Bites and scratches from animals and humans allow the inoculation of
microorganisms that are commonly found in the animal’s oral cavity, nose or
nail.

BITE WOUND INFECTIONS (Cont..)
49
▰ They cause a range of infections such as:
 Lodging of the organisms on the wound surface - bite-wound infections
 Can breach skin barrier and penetrate into the deeper tissue
 Invasion of lymphatics and blood - various systemic infections -
bacteremia, meningitis, brain abscess, and endocarditis.
 Rarely, infection of the cutaneous nerves can carry the organism to CNS
(e.g. rabies causing encephalitis).

Dog Bites
50
▰ Dog bites - 80% of all animal-bite wounds, of which about 15–20% become
infected.
▰ Age/gender: Victims - often children than adults, and males than females
▰ Site: Upper extremity, except for children <4 years - head and neck region

Dog Bites (Cont..)
51
Microbiology:
▰ Common aerobes - β-hemolytic streptococci, Pasteurella species,
Staphylococcus, Eikenella corrodens, and Capnocytophaga canimorsus
▰ Many wounds also include anaerobic bacteria - Actinomyces, Fusobacterium,
Prevotella, and Porphyromonas species
▰ Organisms causing systemic diseases: Rabies and tetanus.

Cat Bites
52
▰ Compared to dog bite, they are also at a higher risk of causing penetrating
injury leading septic arthritis and osteomyelitis (especially in the hand); owing
to their narrow, sharp canine teeth
▰ Victims of cat bite are more often women than men

Cat Bites (Cont..)
53
▰ Microbiology: The organism implicated in cat-bite wound infections is usually
mixed, from cat’s oropharynx; similar to that of dog bite

Human Bites
54
▰ Human bites may take place during
fights, domestic abuse, sexual activity or
healthcare workers caring for patients.
▰ Types of human bites:
 Occlusional injuries
 Clenched-fist injuries
Clenched-fist injuries

Human Bites (Cont..)
55
Microbiology:
▰ Common aerobic isolates - viridans streptococci, S. aureus, Eikenella
corrodens (common in clenched-fist injury), and Haemophilus influenzae
▰ Anaerobic species - Fusobacterium nucleatum and Prevotella, Porphyromonas,
and Peptostreptococcus species

Other Animal Bites
56
▰ Rat bite infections
▰ Snakebites
▰ Bites from Old World monkeys
▰ Bites of seals

Laboratory Diagnosis for Bite Wound Infections
57
▰ The best material for culture - purulent exudate aspirated from the depth of
the wound or samples obtained during surgery .
▰ Most common specimen - wound swab - not suitable for anaerobic culture,
unless immediately dipped into an anaerobic transport media

Laboratory Diagnosis for Bite Wound Infections
(Cont..)
58
▰ Gram-stained smears - prepared and examined
▰ For aerobic cultures, a minimum of blood, MacConkey and chocolate agar
should be inoculated
▰ Anaerobic culture is necessary if abscesses, devitalized tissue, or foul-
smelling exudate is present.

Pasteurellosis
59
▰ Pasteurella species - harbored as normal flora in the oral cavity of cats and
dogs.
▰ Hemorrhagic septicemia in animals.
▰ Pasteurella multocida - most common species infecting man.

Pasteurellosis (Cont..)
60
▰ Clinical features:
▰ Affected area of bite becomes red, swollen and painful with regional
lymphadenopathy and low grade fever
▰ More serious cases - bacteremia , osteomyelitis or endocarditis or meningitis.

Pasteurellosis (Cont..)
61
▰ Laboratory diagnosis: P. multocida - gram-negative coccobacillus, readily
grows in culture media. Identification - biochemically or through automated
methods - MALDI-TOF or VITEK
▰ Treatment: Penicillin G or amoxicillin-clavulanate

Capnocytophaga Infection
62
▰ Several species - C. ochracea, C. gingivalis and C. sputigena - human mouth
flora.
▰ Occasionally cause periodontal diseases, and sepsis/meningitis in
immunocompromised hosts
▰ C. canimorsus and C. cynodegmi - commensals in mouth of dogs

Capnocytophaga Infection (Cont..)
63
▰ Laboratory diagnosis: Fusiform or filamentous gram-negative coccobacilli
▰ Capnophilic (require CO2), grow in enriched media (e.g. blood agar), and
produce orange-pigmented colonies. Grow slowly - 14 days
▰ Identification - biochemically or through automated methods - MALDI-TOF or
VITEK.

Capnocytophaga Infection (Cont..)
64
Treatment:
▰ As they produce β-lactamases, β lactam/ β-lactam inhibitor combination -
ampicillin-sulbactam is used as the drug of choice.

Rat-bite Fever
65
▰ Rat-bite fever (RBF) - septic fever, petechial rashes, and painful polyarthritis
with frequent relapses.
▰ Caused by either of the two pathogens: (1) Streptobacillus moniliformis, and
(2) Spirillum minus.

Rat-bite Fever (Cont..)
66
Transmission:
▰ Transmitted by contact with rodents carrying these bacteria
▰ Consumption of food or water contaminated with the urine and droppings of
rodents carrying the bacteria - Haverhill fever or epidemic arthritic erythema

67
▰ Streptobacillus moniliformis: Causes RBF in North America
 Gram-negative, highly pleomorphic non-motile bacilli, arranged in chains
and tangled filaments with bulbous swellings. Tendency to form L-form
 Isolated from blood, synovial fluid and other infected tissues

68
▰ Spirillum minus: Causes RBF in Asia (known as Sodoku)
 Rigid, spirally coiled motile bacilli
 Doesn’t grow in artificial media.
▰ Treatment: Penicillin

Questions:
69
▰ Q1. Plague is transmitted by:
a. Rat flea
b. Soft tick
c. Hard tick
d. Louse

Questions:
70
▰ Q2. Rat bite fever is caused by:
a. Borrelia recurrentis
b. Streptobacillus moniliformis
c. Yersinia pestis
d. Leptospira

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