Lec 5 Infectious Disease

8/12/2019 Lec 5 Infectious Disease

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A Medical Laboratory Science Approach

by Andre Karl S. Faculin, RMT


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Food-borne Bacterial diarrhea

Hepatitis A & E Typhoid fever

Water-contact Leptospirosis

Vector-borne Dengue

Malaria

Source: CIA World Factbook


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The diseases which spread from one personto another through contaminated food,

water or contact or through insects, animalsetc. are called the communicable diseases.These are caused by different causativeagents (pathogens).


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Water and Food-borne DiseasesTyphoid feverHepatitis virusesCholera

Amebic dysenteryBacillary dysentery


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Air-borne/ Droplet DiseasesPulmonary tuberculosis

ChickenpoxMeaslesSARS

PneumoniaDiphtheriaMumps


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Vector-borne DiseasesDengue

MalariaZoonotic DiseasesRabiesAnthraxFoot and Mouth diseaseBird fluMad cow disease


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Sexually transmitted DiseasesSyphilis

AIDSNon-gonococcal urethritisHerpes simplex

GonorrheaHepatitis B


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1. Chicken pox>Pathogen : Chicken pox virus (varicella-zooster virus); a herpes virus (Herpesviridae);

human herpesvirus 3; DNA Virus>Mode of transmission :By contact or through scabs>Incubation period : 12-20 days

>Symptoms(i) Fever, headache and loss of appetite(ii) Dark red-coloured rash on the back and chest

which spreads on the whole body.

(iii) Later, rashes change into vesicles.


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(iV) After few days these vesicles start dryingup and scabs (crusts) are formed.

(v) These scabs start falling (infective stage)>Prevention and cure

Precautions must be taken as follows:

(i) The patient should be kept in isolation.(ii) Clothing, utensils, etc. used by the patientshould be sterilized.

(iii) Fallen scabs should be collected and burnt.*One attack of chicken pox gives life longimmunity to the person recovered from thisdisease!


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Chicken PoxHighly contagiousGenerally dx of childhood

Spread by inhalation ofinfected droplets orcontact with lesions after10-20 daysFever/malaise mild in

childrenPruritic rash evolvescentrifugally beginningon face/scalp/trunk lesserdegree on extremities

ShinglesAfter primary infectionvirus remains dormant innervous tissuePain often severe, mayprecede rashLesions follow any nerveroot distribution typically thoracic &lumbar


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Typical isolated rash in shingles

In severe cases of shingles, the lesions coalesce,forming a disfiguring carpet of scabs andsometimes the rash leaves permanent scars


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Prevention and cure(i) The patient should be kept in isolation.

(ii) Cleanliness should be maintained.(iii) Antibiotics check only the secondaryinfections which can easily occur.


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Kopliks spots on palate due to pre-eruptivemeasles on day 3 of the illness


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Classic day-4 rashwith measles


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3. Poliomyelitis>Pathogen : Polio Virus; RNA virus of the FamilyPicornaviridae>Mode of transmissions : Virus enters inside thebody through food or water.>Incubation period : 7-14 days>Symptoms

(i) The virus multiplies in intestinal cells and then reachesthe brain through blood.

(ii) It damages brain and nerves and causes infantileparalysis.

(iii) Stiffness of neck, fever, loss of head support.>Prevention and CurePolio vaccine drop (oral polio vaccine, OPV) are given

to children at certain intervals.


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4. Rabies (also called hydrophobia)>Pathogen : Rabies virus; eRNA virus in the FamilyRhabdoviridae>Mode of Transmission : Bite by a rabid dog.>Incubation period : 10 days to 1-3 months dependingupon the distance of bite from Central Nervous System(CNS), that is the brain or spinal cord.>Symptoms

(i) Severe headache and high fever.(ii) Painful contraction of muscles of throat and chest.

(iii) Choking and fear of water leading to death.>Prevention and Cure(i) Compulsory immunization of dogs.(ii) Killing of rabid animals.(iii) Anti-rabies injections or oral doses are given to the

person bitten by a rabid animal.


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5. Hepatitis>Pathogen : Hepatitis viruses.>Mode of Transmission : Mainly throughcontaminated water, also parenterally.>Incubation Period : Generally 15-160 days.>Symptoms

(i) Body ache.(ii) Loss of appetite and nausea.(iii) Eyes and skin become yellowish, urine deep yellow

in color (due to bile pigments).(iv) Enlarged liver.

>Prevention and Cure(i) Hepatitis B vaccine(ii) Proper hygiene is to be observed.

(iii) Avoid taking fat rich substances


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Type A Hepatitis (HAV Infection, InfectiousHepatitis, Epidemic Hepatitis)

Hepatitis A virus (HAV); a linear ssRNA virus Fecal-oral transmission

Disease:- Abrupt onset- varies in clinical severity from mild illness

lasting 1-2 weeks to a severe, disablingdisease lasting several months

- no chronic infection


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Type B Hepatitis (HBV Infection, Serum Hepatitis) Hepatitis B virus (HBV); an enveloped, circular

dsDNA virus Sexual transmission or household contact with an

infected person; injected drug use; tattooing; needlesticksDisease:- Usually has an insidious (gradual) onset- severity ranges from inapparent cases to

fulminating, fatal cases- chronic infections occur which may lead to

cirrhosis or hepatocellular carcinoma


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Type C Hepatitis (HCV Infection, Non-A Non-BHepatitis)

Hepatitis C virus (HCV); an enveloped, linearssRNA virus

Primarily parenterally transmitted; rarelysexually

Disease:- Usually an insidious onset- 50%-80% of patients develop a chronic

infection & may lead to cirrhosis or

hepatocellular carcinoma


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Type D Hepatitis (HDV Infection, DeltaHepatitis) Hepatitis D virus (HDV, delta virus); an

enveloped, circular ssRNA viral satellite; co -infection with HBV is necessary

Exposure to infected blood and body fluids, etc.Disease:

- Usually has an abrupt onset- May progress to a chronic and severedisease


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Type E Hepatitis Hepatitis E virus (HEV); a non-enveloped, ssRNA

virus Fecal-oral transmission; primarily fecally

contaminated drinking water; also person-to-person

Disease:- Similar to Hepatitis A- evidence of a chronic form


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Type G Hepatitis Hepatitis G virus (HGV); a linear ssRNA virus

Parenteral transmissionDisease:- Can cause chronic hepatitis


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6. InfluenzaInfluenza, commonly known as flu is anillness caused by viruses that infect the

respiratory tract. Compared to common cold,influenza is a more severe illness.>CausesInfluenza is caused by a virus which attacksour bodys cells, resulting in various effectsdepending on the strain of the virus.


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>SymptomsTypical symptoms of influenza include:(i) fever (Usually 100 F to 103 F in adults and often

even higher in children).(ii) respiratory tract infection symptoms such as, cough,

sore throat, running nose, headache, pain in themuscles, and extreme fatigue.Although nausea and vomiting and diarrhea cansometimes accompany Influenza infection, especially

in children, gastrointestinal symptoms are rarelyprominent.Most people who get flu, recover completely in 1 to 2weeks, but some people develop serious andpotentially life-threatening complications, such as

pneumonia.


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>Treatment and Control(i) Much of the illness and death caused by

influenza can be prevented by annual influenzavaccination. Influenza vaccine is specificallyrecommended for those who arc at high risk forcomplications with chronic diseases of the heart,lungs or kidneys, diabetes, or severe forms ofanemia.

(ii) The persons suffering from influenza shoulddrink plenty of fluids take symptom relief withparacetamol, aspirin (not in children under theage of 16) or ibuprofen etc. as recommended bythe doctor.Consult doctor immediately for treatment.


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7. DengueDengue is an acute fever caused by virus. It is of twotypes:

(i) Dengue fever,(ii) Dengue hemorrhagic fever.Dengue fever is characterized by an onset of sudden

high fever, severe headache, pain behind the eyesand in the muscles and joints.

Dengue hemorrhagic fever is an acute infectious viraldisease. It is an advanced stage of dengue fever. It ischaracterized by fever during the initial phase andother symptoms like headache, pain in the eye, jointpain and muscle pain, followed by signs of bleeding,red tiny spots on the skin, and bleeding from nose andgums.


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Dengue spreads through the bite of aninfected Aedes aegypti mosquito.The transmission of the disease occurs whena mosquito bites an infected person andsubsequently bites a healthy person. In doingso, it transmits blood containing the virus to

the healthy person and the person becomesinfected with dengue.The first symptoms of the disease occurabout 5 to 7 days after the infected bite.


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Aedes mosquito rests indoors, in closets andother dark places, and is active during day

time. Outside, it rests where it is cool andshaded. The female mosquito lays her eggs instagnant water containers such as coolers,tires, empty buckets etc., in and aroundhomes, and other areas in towns or villages.These eggs become adults in about 10 days.


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Incubation periodThe time between the bite of a mosquitocarrying dengue virus and the start ofsymptoms averages 4 to 6 days, with a rangeof 3 to 14 days.

Diagnosis

Diagnosis is made through blood tests byscanning for antibodies against dengueviruses. In addition the blood platelets countsalso drastically reduce in the infected person.


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>Symptoms of Dengue fever(i) Sudden onset of high fever, generally 104-

105 F (40 C), which may last 4-5 days.(ii) Severe headache mostly in the forehead.(iii) pain in the joints and muscles, body aches.(iv) Pain behind the eyes which worsens with

eye movement.(v) Nausea or vomiting.


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Symptoms of Dengue Hemorrhagic FeverThese include symptoms similar to denguefever, plus other symptoms such as:

(i) Severe and continuous pain in the abdomen.(ii) Rashes on the skin.(iii) Bleeding from the nose, mouth, or in the

internal organs.(iv) Frequent vomiting with or without blood.(v) Black stools due to internal bleeding.(vi) Excessive thirst (dry mouth).(vii) Pale, cold skin, weakness.


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Following steps can be taken to prevent spreadof dengue fever:

(i) Avoid water stagnation for more than 72

hours so that the mosquitoes do not breedthere.

(ii) Prevent mosquito breeding in stored water

bodies, like ponds, wells etc.(iii) Destroy discarded objects like old tires,bottles, etc. as they collect and store rainwater.


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(iv) Use mosquito repellents and wear longsleeved clothes to curtail exposure.

(v) Use mosquito nets, also during daytime.(vi) Avoid outdoor activities during dawn ordusk when these mosquitoes are most active.

(vii) Patients suffering from dengue fever mustbe isolated for at least 5 days.

(viii)Report to the nearest health centre for anysuspected case of Dengue fever.


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8. Genital Herpes [HSV-1 and HSV-2]

9. Genital Warts (HPV)


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1. Tuberculosis>Pathogen : A bacterium ( Mycobacteriumtuberculosis).>Mode of Transmission : airborne-discharged

through sputum, cough, sneeze, etc. of theinfected person.>Incubation period : 2-10 weeks during whichthe bacteria produce a toxin, tuberculin.>Symptoms(i) Persistent fever and coughing.(ii) Chest pain and blood comes out with thesputum.(iii) General weakness


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Acid fast stained sputum positive for M. tuberculosis (1000x)


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Prevention and Cure(i) Isolation of patient to avoid

spread of infection.(ii) BCG vaccination is given tochildren as a preventive measure.

(iii) Living rooms should be airy, neatand with clean surroundings.

(iv) Antibiotics be administered astreatment.


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2. Typhoid Fever>Pathogen : A bacillus/rod-shapedbacterium ( Salmonella typhi)

>Mode of transmission : Throughcontaminated food and water>Incubation period : About 1-3 weeks


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Symptoms(i) Continuous fever, headache, slow pulse rate.

(ii) Reddish rashes appear on the belly.(iii) In extreme cases, ulcers may ruptureresulting in death of the patient.


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Other SymptomsInvades intestinal epithelium tissue

Ulcerations Bloody stools but little diarrhea Blood invasion Fever; delirium Blood vessel hemorrhaging Rose-colored spots on the abdomen Bowel perforation Gall-bladder infection


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How to

ControlTyphoid

Mary?


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3. CholeraIt often breaks out among crowded and areaswith poor sanitary conditions.

>Pathogen : Comma shaped bacterium(Vibrio cholerae)>Mode of transmission : Contaminated

food and water. House - fly is the carrier.>Incubation period : 6 hours to 2-3 days.


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Symptoms(i) Acute diarrhea, rice

watery stool(ii) Muscular cramps(iii) Loss of minerals through

urine

(iv) Dehydration leading todeath


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Other symptomsGastroenteritis with extensive severe diarrhea

Cholera enterotoxin Toxin blocks water reabsorption by inhibiting the

anion active transport mechanism in largeintestinal epithelium

Rice water stools Dehydration & death

Recent epidemic due to spread of new drug-resistant strain


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4. DiphtheriaThis disease generally occurs in children of 1-5 years of age.>Pathogen : Rod-shaped bacterium(Corynebacterium diphtheriae)>Mode of Transmission : Through air

(droplet infection)>Incubation period : 2-4 days


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Corynebacterium diphtheriae (1000x)


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>Symptoms(i) Slight fever, sore throat and general

indisposition.(ii) Oozing semisolid material in the throat

which develops into a tough membrane. Themembrane may cause clogging (blocking) ofair passage, resulting into death.


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>Prevention and cure(i) Immediate medical attention should be

given.(ii) Babies should be given DPT vaccine.(iii) Sputum, oral and nasal discharges of the

infected child should be disposed off.(iv) Antibiotics may be given under doctors

supervision.(v) Isolation of the infected child.


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5. LeprosyPathogen : A bacterium ( Mycobacterium

leprae)Mode of transmission : Prolonged contact

with the infected person. Nasal secretionsare the most likely infectious material for

family contacts.Incubation period : 1-5 years


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Symptoms(i) Affects skin.(ii) Formation of nodules and ulcer.(iii) Scabs and deformities of fingers

and toes.(iv) Infected areas lose sensation.


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Prevention and Cure(i) The children should be kept away from

parents suffering from leprosy.(ii) Some medicine may arrest the disease and

prevent from spreading.


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6. Chlamydia7. Gonorrhea8. Syphilis9. Chancroid10. Granuloma inguinale11. Lymphogranuloma venereum (LGV)12. Rickettsial diseases13. Lyme disease14. Plague15. Tularemia16. Listeriosis17. Tetanus


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MutualismCommensalism

ParasitismParasites Endoparasite versus Ectoparasite

Obligate versus Facultative


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HostsDefinitiveIntermediateAccidental

Dead-end


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1. Malaria>Pathogen : Malarial parasite (different

species of Plasmodium)>Mode of transmission : By bite of female

Anopheles mosquitoes>Incubation period : Approximately 12 days

PROTOZOANS


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Symptoms(i) Headache, nausea and muscular pain.(ii) Feeling of chilliness and shivering followed

by fever which becomes normal along withsweating after some time.

(iii) The patient becomes weak and anaemic.(iv) If not treated properly secondary

complications may lead to death.


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Asexualphase in

humans assporozoiteenters

Sexualphase withsporozoiteformation inthemosquito

Gametocytesproduced andingested bymosquito

Liver phase(sporozoitesinvade &merozoitesproduced

RBCs infected by merozoites from the liver


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>Prevention and cure(i) Fitting of double door and windows (with wire

mesh) in the house to prevent entry of

mosquitoes.(ii) Use of mosquito net and mosquito repellents.(iii) No water should be allowed to collect in

ditches or other open spaces to preventmosquito breeding.

(iv) Sprinkling of kerosene oil in ditches or otheropen spaces where water gets collected.

(v) Antimalarial drugs to be taken.


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2. Amoebiasis (Amoebic dysentery)>Pathogen : Entamoeba histolytica>Mode of transmission : Contaminated food

and water>Symptoms(i) Formation of ulcers in intestine.(ii) Feeling of abdominal pain and nausea.(iii) Acute diarrhoea and mucus in stool.


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Entamoeba histolytica cyst (left) and trophozoite (right)

Life Cycle of Entamoeba histolytica


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>Prevention and cure(i) Proper sanitation should be maintained.(ii) Vegetables and fruits must be properly

washed before eating.(iii) Antibiotics may be given to the patients.


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3. Leishmaniasis4. Amebic conjunctivitis and

keratoconjunctivitis5. Toxoplasmosis6. Trichomoniasis7. Trypanosomiasis8. Babesiosis9. Primary amebic meningoencephalitis10. Granulomatous amebic encephalitis


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1. Filariasis>Pathogen : Filarial worm ( Wuchereria bancrofti,Brugia malayi)>Mode of transmission : Bites of mosquitoes - Aedes and Culex.>Symptoms

(i) Fever(ii) Collection of endothellial cells and metabolites in the

wall of lymph vessels.(iii) Swelling takes place in certain parts of the body likelegs, breasts, scrotum, etc.(iv) Swelling of legs which appear as legs of elephant, so

this disease is also called elephantiasis

METAZOANS


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Elephantiasis


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>Prevention and cure(i) Mesh doors and windows in the house to

check the entry of mosquitoes.(ii) The water collected in tanks or other articles

should be properly covered.(iii) Sprinkling of kerosene in ditches, etc.(iv) Drugs may be administered.


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2. HelminthsAdults are large, multicellular animals with specialized tissues &organsAdult worms mate & produce fertilized eggs that hatch intolarvae that mature in several stages to adults (the sexes may separateor hermaphroditic)Hosts

adults live in the definitive hosteggs & larvae may develop in the same host, external environment, orintermediate hosta transport host experiences no parasitic development

Pathology arises from worms feeding on & migrating throughtissues and accumulation of worms & worm products


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2. Helminthsa. Roundworms (Nematodes)

Filamentous with protective cuticles, a complete

digestive tract, & separate sexes Ascaris lumbricoides Trichuris trichiura (whipworm) Enterobius vermicularis (pinworm)

Hookworms Strongyloides stercoralis Trichinella spiralis Filarial worms


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Ascaris spends its larval & adult stages inhumans & releases embryonic eggs in feces,which are spread to other humansIngested eggs hatch into larvae & burrowthrough the intestine into circulation & travelto the lungs & pharynx & are swallowed.Adult worms complete cycle in intestines


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Ascaris lumbricoides worms retain motility butdo not attach to the intestinesSevere inflammatory reactions mark themigratory route,Allergic reactions can occurHeavy worm loads can retard physical &mental development


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2.a.2. Roundworm zoonoses(Toxocara canis, Toxocara cati )

Dog and Cat Roundworms (toxocariasis)Est. 10,000 new cases of roundworm infectionoccur in children every year, most often as a resultof eating dirt contaminated with animal fecesMost human infections are mild enough to go

unnoticed and apparently produce no permanentdamageHowever, toxocariasis can lead to:

Visceral Larval Migrans (VLM)

Ocular Larval Migrans (OLM)


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Flashlight Test : At night, thefemale adult worms deposit theireggs outside the rectum or analarea.

Cellophane tape/ Scotch tapetest for pinoworms


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2.a.5. HookwormsCharacteristic curved ends & hooked mouthsEndemic to tropics and subtropics

Necator americanus & Ancylostoma duodenaleHumans shed eggs in feces, which hatch intofilariform (threadlike) larvae & burrow into theskin of lower legs

Local irritation ground itch


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Larvae travel from blood to lungs, proceed upto the bronchi and throat, and are swallowed.Worms mature and reproduce in small

intestine and complete its cycleMay cause pneumonia, nausea, vomiting,cramps & bloody diarrheaBlood loss can be significant

Microcytic Anemia


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Faculin, et al. Soil-Transmitted Helminthiasis Among School-Age Children of Barangay RizalPala-Pala I, Iloilo City. (2013). University ofSan Agustin: Iloilo City.
http://localhost/var/www/apps/conversion/tmp/Research%20Presentation%20(JAMLS%20DoKs).pptx


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SEE HANDOUTS


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SuperficialCutaneous

SubcutaneousSystemicOpportunistic


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SkinDermatophytosis (Tinea [Ringworm] infections) Microsporum Epidermophyton Trichophyton


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Lower Respiratory TractCoccidioidomycosis (Valley fever)CryptococcosisHistoplasmosisPneumocystis pneumonia (PCP)


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Oral CavityThrush


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Cryptococcal Meningitis


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End of Lec 5Medical Laboratory Scientist

Lec 5 Infectious Disease

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