Date: 27.06.

2024

Live MCQTM
Special BCS Health
Lecture No-24

Medicine-09

Topic:
Infectious Diseases & STDs

Mentor:
Dr. Mohammad Rasel
Registrar (Medicine)
Mymensingh Medical College Hospital
Important Topics:
1. Enteric Fever
2. Dengue
3. Tuberculosis
4. Leprosy
5. Kala-azar
6. Malaria
7. Acute Diarrhoea

Enteric Fever
1. Enteric fevers are caused by infection with Salmonella enterica
serotypes Typhi and Paratyphi A, B and C
2. The temperature rises in a stepladder fashion for 4 or 5 days with
malaise, increasing headache, drowsiness and aching in the limbs
3. Chronic carrier state is common in people of age > 50 years, more in
females
4. Usual site is gallbladder and may be associated with gallstones
Clinical Features

Signs
• Coated tongue
• Relative bradycardia
• Splenomegaly ( Just Palpable)
• Caecal gurgling.
Investigations
• In the 1st week, diagnosis may be difficult because, in this invasive stage
with bacteraemia, the symptoms are those of a generalised infection
without localising features
• Typically, there is a leucopenia.
• Blood culture establishes the diagnosis and multiple cultures increase
the yield
• Stool cultures are often positive in the second and third weeks
• The Widal test detects antibodies to the O and H antigens but is not
specific.

Treatment
• Fluoroquinolones are the drugs of choice, but resistance is common
• Azithromycin (500 mg once daily) is an alternative when fluoroquinolone
resistance is present
• Inj. Ceftriaxone 2g IV 12 hourly for 14 days is commonly used regimen.
• Pyrexia may persist for up to 5 days after the start of specific therapy
• Chronic carriers were formerly treated for 4 weeks with ciprofloxacin but
may require an alternative agent and duration, as guided by
antimicrobial sensitivity testing, Cholecystectomy may be necessary

Complications

Paratyphoid Fever
• The course tends to be shorter than that of typhoid fever and the onset
is often more abrupt, with acute enteritis
• The rash may be more abundant and the intestinal complications less
frequent

Prevention
Improved sanitation and living conditions reduce the incidence of typhoid
Travellers to countries where enteric infections are endemic should receive
typhoid vaccination
In young children a tetanus conjugate vaccine containing Vi polysaccharide
conjugated to tetanus toxoid has over 80% efficacy and is superior to older
inactivated injectable or oral live attenuated vaccines.
Dengue
The word dengue is derived from African word denga: meaning fever with
hemorrhage.
Is caused by virus transmitted of bites of mosquito aedes.
• Dengue virus, which has 4 distinct serotypes, i.e. DENV-1, DENV-2, DENV-
3, DENV-4 is transmitted by Aedes aegypti and Aedes albopictus to
human
• Infection with one serotype confers lifelong immunity to that serotype
and cross immunity to other serotypes for 2-3 months only
Warning Signs
Kala-azar
Clinical Features
The majority of infections remain asymptomatic.
In visceral disease, the spleen, liver, bone marrow and lymph nodes are
primarily involved
The first sign of infection is high fever, usually accompanied by rigor and
chills.
Fever intensity decreases over time and patients may become afebrile for
weeks to months.
This is followed by a relapse of fever, often of lesser intensity.
• Splenomegaly develops quickly in the first few weeks and becomes
massive as the disease progresses.
• Moderate hepatomegaly occurs later.
• Lymphadenopathy is common in Africa, the Mediterranean and South
America but is rare in South Asia.
• Blackish discoloration of the skin, from which the disease derived its
name, kala-azar (the Hindi word for ‘black fever’), is a feature of
advanced illness but is now rarely seen.
• Pancytopenia is common.
• Moderate to severe anaemia develops rapidly and can cause cardiac
failure.
• Thrombocytopenia, often compounded by hepatic dysfunction, may
result in bleeding from the retina, gastrointestinal tract and nose.
• In advanced illness, hypoalbuminemia may manifest as pedal oedema,
ascites and anasarca (gross generalized oedema and swelling).

Investigations
Pancytopenia is the dominant feature, with granulocytopenia
Polyclonal hypergammaglobulinemia, chiefly IgG followed by IgM, and
Hypoalbuminemia are seen later
Demonstration of amastigotes (Leishman–Donovan bodies) in splenic
smears is the most efficient means of diagnosis, with 98% sensitivity
Safer methods, such as bone marrow or lymph node smears, are less
sensitive but are frequently employed.
Parasites may be demonstrated in buffy coat smears, especially in
immunosuppressed patients.
Sensitivity is improved in specialised laboratories by culturing the aspirate
material or by using PCR for DNA detection and species identification.
Serodiagnosis, by ELISA or immunofluorescence antibody test
Equally efficient rapid immunochromatographic k39 (RK39) strip test have
become popular.
These tests remain positive for several months to years after cure has been
achieved, so do not predict response to treatment or relapse.

Case Definition
The diagnosis of Kala-azar will be based on the following criteria in a
symptomatic case.
History of fever for more than 2 weeks
Residing/ traveling in endemic areas
Any one of the following symptoms and signs:
1. Splenomegaly
2. Weight loss
3. Anemia
And ‘rk39’ test (+) positive.

PKDL should be considered if all of the following features are present-

• Residing / travelling in the endemic areas
• History of treatment for Kala-azar any time in the past.
• Suggestive skin lesion without loss of sensation, which may be macular
papular, nodular or mixed.
• Exclusion of other causes of skin disease e.g. Leprosy, Vitiligo, Pityriasis,
Ring worm etc.
• ‘rk39’ positive/ Slit skin smear positive/ PCR positive.
Prevention & Control
• Sandfly control through insecticide spray is very important.
• Mosquito nets or curtains treated with insecticides will keep out the
tiny sandflies.
• In endemic areas with zoonotic transmission, infected or stray dogs
should be destroyed.
• In areas with anthroponotic transmission, early diagnosis and
treatment of human infections, to reduce the reservoir and control
epidemics of VL, is extremely important.

Malaria
▪ Protozoal infection caused by:-
➢ Plasmodium falciparum
➢ Plasmodium vivax
➢ Plasmodium ovale
➢ Plasmodium malariae
➢ Plasmodium knowlesi
▪ In Bangladesh 82% of the total annual reported cases are due to
Plasmodium falciparum.
▪ The remaining cases are due to Plasmodium vivax, and few are due to
mixed infection.

P. vivax and P. ovale may persist in liver cells as dormant form hypnozoites
capable of developing into merozoites months or years later
Thus the first attack of clinical malaria may occur long after the patient has
left the endemic area, and the disease may relapse after treatment with
drugs that only kill the erythrocytic stage of the parasite
P. falciparum, P. knowlesi and P. malariae have no persistent
exoerythrocytic phase but recrudescence of fever may result from
multiplication of parasites in red cells that have not been eliminated by
treatment and immune processes
Red cells infected with malaria undergo haemolysis which is most severe
with P. falciparum that invades red cells of all ages P. vivax and P. ovale
preferentially invade younger cells, and P. malariae normoblasts, so that
infections remain lower
Anaemia may be profound and is worsened by dyserythropoiesis,
splenomegaly and depletion of folate stores

Investigation
▪ WHO recommends prompt malaria diagnosis, either by microscopy
or malaria rapid diagnostic test (RDT), whenever malaria is suspected
▪ In a Giemsa-stained thick film, erythrocytes are lysed, releasing all
blood stages of the parasite
▪ This, as well as the fact that more blood is used in thick films, facilitates
the diagnosis of low-level parasitemia
A thin film is essential to confirm the diagnosis, species and, in P.
falciparum infections, to quantify the parasite load (by counting the
percentage of infected erythrocytes)
 Tuberculosis
▪ Causative Organism: Three Types of Mycobacteria
1. Mycobacterium tuberculosis (causes TB in human)
2. Mycobacterium bovis (endemic in cattle, rarely infects human).
3. Atypical mycobacteria.

▪ Sites of tuberculosis: Lung, lymph node, spine (Pott’s disease), kidney,

intestine (ileocaecal), fallopian tube, meninges, pericardium.
Whom to suspect
▪ Any patient with cough for two weeks or more with or without
✓ Respiratory Symptoms: SOB, Chest pain, Hemoptysis
✓ General Symptoms: Weight loss, Fever, Night sweats, Loss of appetite
▪ Contacts of sputum positive cases with cough of any duration
▪ Presumptive extrapulmonary TB
▪ HIV positive patient having cough of any duration
Tools for diagnosis of TB
➢ CBC
➢ Sputum smear examination
➢ Radiological (X-ray) examination of the lungs
➢ Culture of TB bacilli
➢ Rapid Molecular Diagnostic Tests (RMDT)
✓ Gene Xpert
✓ Line Probe Assay (LPA)
➢ FNAC, Biopsy and Histopathology for EP TB
➢ IGRA
Leprosy
▪ M. leprae has tropism for Schwann cells and skin macrophages
▪ The clinical manifestations are determined by the degree of the
patient’s cell-mediated immunity (CMI) towards M. leprae
▪ The most common skin lesions are macules or plaques
▪ Peripheral nerve trunks are affected at ‘sites of predilection
▪ The diagnosis is clinical, made by finding a cardinal sign of leprosy and
supported by detecting acid-fast bacilli in slit-skin smears or typical
histology in a skin biopsy
Amoebiasis
▪ Amoebiasis is caused by Entamoeba histolytica
▪ E. histolytica causes amoebic dysentery or liver abscess
▪ Cysts of E. histolytica are ingested in water or uncooked foods
contaminated by human faeces. Infection may also be acquired
through anal/oral sexual practices
▪ The parasite invades the mucous membrane of the large bowel,
producing lesions that are maximal in the caecum but extend to the
anal canal. These are flask-shaped ulcers, varying greatly in size and
surrounded by healthy mucosa
▪ Chocolate-brown (said to resemble anchovy sauce) is characteristic
▪ Microscopic examination of the stool and exudate can reveal motile
trophozoites containing red blood cells
▪ Sigmoidoscopy may reveal typical flask-shaped ulcers, which should
be scraped and examined immediately for E. histolytica
▪ Confirmation is by ultrasonic scanning
▪ Aspirated pus from an amoebic abscess has the characteristic
chocolate-brown appearance but rarely contains free amoebae
▪ Intestinal and early hepatic amoebiasis responds quickly to oral
metronidazole (800 mg 3 times daily for 5–10 days) or other long-
 acting nitroimidazoles like tinidazole or ornidazole (both in doses of 2
g daily for 3 days)
▪ Nitazoxanide (500 mg twice daily for 3 days) is an alternative drug
▪ Either diloxanide furoate or paromomycin, in doses of 500 mg orally 3
times daily for 10 days after treatment, should be given to eliminate
luminal cysts

Giardiasis
▪ Its flagellar trophozoite form attaches to the duodenal and jejunal
mucosa causing inflammation
▪ non-bloody diarrhoea
▪ Duodenal or jejunal aspiration by endoscopy gives a higher diagnostic
yield
▪ Treatment is with a single dose of tinidazole 2 g, metronidazole 400
mg 3 times daily for 10 days, or nitazoxanide 500 mg orally twice daily
for 3 days

Filariasis
▪ Filariasis is transmitted by bite of infected culex mosquito
▪ Wuchereria bancrofti is the organism
▪ Acute lymphangitis
▪ Chronic lymphatic disease – Elephantiasis
▪ CBC shows eosinophilia.
▪ Serum IgE—high.
▪ ICT for filaria.
▪ Blood film at night, to see microfilariae
▪ Diethylcarbamazine (DEC)—6 mg/kg in three divided doses for 2
weeks
Gonorrhea
▪ It is a sexually transmitted disease (STD) caused by Neisseria
gonorrhoeae, a Gram negative diplococcus
▪ Mode of Transmission-Sexually from partner, Neonate exposed to
infected secretions in birth canal
▪ Urethral discharge—copious, mucopurulent or purulent
▪ In Neonate- Ophthalmia neonatorum
▪ Gram stain - Gram negative diplococci seen on microscopy of smear
from infected site
Syphilis