TYPHUS

Introduction Typhus fever is an infective disease of world wide

distribution. The causative organisms of all types of typhus

are different Rickettsiae. The vectors of the different forms of typhus are

also different. Based on the vectors , 4 kinds of typhus fever are

present.1. Louse typhus or Louse - born typhus2. Flea typhus or Flea - borne typhus3. Tick typhus or Tick - borne typhus4. Mite typhus or Mite - borne typhus

Louse typhus or louse-born typhus: vector is louse eg: Epidemic typhus , Brill’s disease , Trench fever

1. Epidemic typhus fever

a. Also known as exanthematic typhus , classical typhus or louse borne typhus

b. World wide distribution ( mainly in Africa )c. The causative organism of epidemic typhus is Rickettsia

prowazeki.d. The vector is the human louse ( Pediculus humanus ).e. The pathogen can survive in the dried faces

Pathogenicity The incubation period of epidemic typhus is 10

– 15 days. Head ache , back pain & limbs pains Sudden rise in temperature , 5th or 6th days

head ache increase Then the characteristic rash called ‘mulberry

rash’ may appear on the chest , abdomen ,inner side of arms and back.

During 2nd week ‘coma vigil’ develops In the absence of recovery death may occur

from heart failure within 2 weeks. Mortality rate ranges from 10 – 100 %

Pediculus humanus Mulberry rash

Flea typhus ( Murine typhus ) The typhus in which the infecting rickettsia is

transmitted by flea. World wide distribution ( unhygienic and rat infected

areas, hence the old names ‘jail fever’ and ‘ship typhus’ )

The causative organism is Rickettsia mooseri and the vector is the rat flea (Xenopsylla cheopis )

Rat serve as the main reservoir of infection. Human louse may act as the transmitter of the Rickettsia from man to man

Pathogenicity : similar to louse typhus mortality rate is very low 1 –

2 %

Xenopsylla cheopis

( Rat flea )

Tick typhus : vector is ticks eg: Rocky mountain spotted fever , tick – bite fever , fievere boutonneuse

1. Rocky mountain spotted fever# this typhus fever is found in many of

the western and eastern states of USA

# the causative agent is Rickettsia rickettsia

# vector wood tick --- Dermacentor andersoni

# dog tick - Dermacentor variabilis

# spring & early summer ticks are highly active

Pathogenicity The incubation period ranges from 3-12 days After 1 or 2 days head ache , back ache & loss

of appetite Rise in temperature up to 41.4⁰ Rashes usually appear during the 2nd to 4th day The temperature settles slowly after 2 or 3

weeks The average mortality rate is 20 %

2. Fievre boutonneuse

Also known as African tick fever or Marseilles fever

Is a mild type of tick typhus , found all over Africa and India & also in the Mediterranean countries

The causative organism is Rickettsia conori The common transmitting agent is the dog tick –

Rhipicephalus sanguineus Symptoms mainly occure in biting area

3. Tick bite fever

Also known as African tick typhus Commonest in S.Africa , E.Africa , Zambia &

Zimbabwe Cattle and dogs to man disease transmitted The disease are similar to Rocky mountain

spotted fever The fever may persist for nearly 2 weeks Mortality rate less than 1%

Mite typhus vector is miteseg: Scrub typhus & Rickettsial

pox1. Scrub typhus

# Also known as tsutsugamushi fever , Japanese river fever or

tropical typhus.# found in japan , Pakistan & Australia # The causative agent of the disease is

Rickettsia tsutsugamushi# transmitted by the larvae of various mites# tick ---- rodents ---- man# the disease common among farmers , field

workers etc..

Pathogenicity

Incubation period of scrub typhus is 5 – 20 days head ache , back ache Small ulcer may develop at the site of mite bite,

associated with the enlargement of lymph glands of the area

Rapid rise in temperature to about 40⁰ C After 4th or 5th day rashes appear on chest ,

abdomen , limbs Decrease the temperature during 3rd week

2. Rickettsial pox Is a mild disease caused by Rickettsia akari Which is transmitted from infected mouse to

man by the mouse mite Allodermanyssus sanguineus

The disease is found in the USA , west and south Africa and Russia

Allodermanyssus sanguineus( mouse mite )

Prophylaxis of typhus fever

The general principle of prophylaxis and curative treatment are the same in all types of typhus

Prophylaxis consists of the control or destruction of the vector

Use of insecticides such as DDT , gammexane etc.. Rat control Wearing of protective clothing to escape from mite

bite is an effective practical method of prophylaxis

Treatment

The administration of chloramphenicol & tetracyclines is the safest method of curative treatment.

The most widely used antibiotic is the long – acting tetracycline doxycycline

A single oral dose of it has been proved to be curative.

YELLOW FEVER

Introduction

Yellow fever also known as “yellow jack “ or vomito amarilli .

Yellow fever virus Is an acute viral disease characterized by fever and

jaundice. It is commonly found in certain tropical areas . The causative organisms of yellow fever is a virus ,

transmitted to man by the mosquito Aedes aegypti . Monkeys serve as important reservoirs of infection in

area where the disease is endemic.

The most common epidemic vector of dengue in the world is the Aedes aegypti mosquito. It can be identified by the white bands or scale patterns on its legs and thorax.

How do you get yellow fever?

The bite of an infected mosquito.

The mosquito injects the yellow fever virus into the victim.

Only female mosquitoes spread yellow fever.

Yellow fever is diagnosed by a blood test.

Pathogenicity

The yellow fever virus present the blood The incubation period is usually 3-5 days but may go up

to 10 days . Severe attack of yellow fever passes through three stages

Stage one : high fever , jaundice , body painStage two : patient feel better that mean starting of

second stageStage three : toxic period

Signs & Symptoms

High fever Chills Headache Muscle aches

Stage One (3-6 days after exposure)

Loss of appetite Nausea Jaundice (yellowing of eyes and skin)The initial symptoms last for nearly three days .then

they may be abate to some extent for a day or two and the patient feels better.this constitute second stage

Signs & Symptoms Stage Two: Remission 3-4 days Recovery possible Stage Three: Toxic period Vomiting Bleeding Hemorrhage Kidney and liver failure coma Heart damage Death

Prophylaxis

Vaccination of all people Migration of people spread the disease Vaccination every 10 years Control mosquito population

Treatment

Curative treatment mainly involves the checking of the symptoms as & when they appear.

Vomiting is allayed by sucking ice or sipping iced water & also by the administration of dilute hydrocynic acid in doses of two drops in water .

Patient must be supplied with sufficient water , mixed with glucose and flavoured with the juice of orange ,lime etc…

Food should be milk , thin soup and similar liquid feed

Yellow Fever Today

Common in West and Central Africa and parts of South America; very rare in U.S.

Preventable by immunization

Treatment: rest and fluids

Dengue fever

Introduction

Also called Break - bone fever , Dandy fever , Three day – fever.

Is viral disease of tropical & sub tropical regions

The disease is transmitted to man by the mosquito Aedes aegypti .

The most common epidemic vector of dengue in the world is the Aedes aegypti mosquito. It can be identified by the white bands or scale patterns on its legs and thorax.

1-2 days

Stagnant water

Pupae

4-5 days

Life cycle of the Aedes Mosquito

Larvae Eggs

2-3 days

Mosquito bites and sucks blood containing the virus from an infected person.

Virus is carried in its body.

And passes the virus to healthy people when it bites them.

Pathogenicity & Symptoms

Dengue is a sudden and short infectious fever . Skin rashes and itching Fever , swellings & pains in joints , skin eruptions

etc.. Joint pain and muscular pain ( symptoms present

last 3 days ) Gradually disappear again 3 or 4 days reappear Recovery slow Death very seldom occurs

Treatment

Aspirin , often with codeine , usually relieves the pains and lowers the temperature.

In more severe cases , pethidine is administered to bring relief

Calamine lotion eases the itching of the rash