Infections and Infestations: The Impact of Invaders Within

Introduction:

Infections are diseases caused by microorganisms such as bacteria, viruses, and fungi. In contrast, infestations are diseases caused by parasites that depend on hosts for nutrition, such as helminths, protozoa, ectoparasites, mites, and pests. Diagnosing infections and infestation is based on history and clinical findings, followed by swab culture, blood tests, and imaging tests.

What Is an Infection?

An infection is the invasion and growth of microorganisms in the body. The microorganisms can be bacteria, fungi, viruses, yeast, etc. Infections can occur anywhere in the body and spread over the body. An infection generally presents with fever and other health issues depending on the site of infection.

How Does Infection Occur?

Infections can be bacterial, viral, fungal, or protozoal.

Bacterial Infections:

Bacterial infections are common, with a few causing serious, recurrent, disseminated, or persistent lesions, especially in immunocompromised individuals (organ transplant patients, HIV/AIDS, cancers) or life-threatening (meningitis), long-term infections (tuberculosis, syphilis). They are often diagnosed on clinical findings followed by smears, cultures, serological testing for immune responses, and nucleic acid examinations. Antibacterial drugs are effective treatment options, but pus drainage is essential. A few examples of bacterial infections include–

• Cholera.

• Diphtheria.

• Gonorrhea.

• Haemophilus.

• Leprosy.

• Plague.

• Salmonella.

• Syphilis.

• Tetanus.

• Staphylococci.

• Streptococci.

• Tuberculosis.

• Typhoid.

• Yersinia.

• Listeria.

• Pneumococci.

Bacterial Infections of the Oral Cavity:

• Periodontal Infections: A gingival abscess may arise from infection. A lateral periodontal abscess can be seen following an impaction of a foreign body or a lateral root canal on a non-vital tooth. They are painful, erythematous, swollen abscesses with pus discharge through a pocket or buccally. Drainage of abscesses along with antibiotics are the treatment of choice.

• Acute Necrotizing Ulcerative Gingivitis (ANUG): ANUG is a non-contagious anaerobic infection caused by the proliferation of fusiform bacteria and Borrelia vincentii. It is commonly seen in young adults, in institutions, armed forces due to poor oral hygiene, smoking, viral respiratory infections, and immune defects like HIV. Characteristics of ANUG include halitosis, bad taste, profuse gingival bleeding, soreness due to gingival ulceration. Treatment involves oral debridement, Metronidazole, and improved oral hygiene.

• Odontogenic Infections: These infections result from pulpitis that causes periapical infection and a dental abscess. They arise from oral microbial flora, primarily anaerobic bacteria. These infections are treated through abscess drainage, root canal or endodontic treatment, incision, or tooth extraction. Analgesics and antibiotics are also indicated.

Nosocomial Infections:

They are hospital-acquired or healthcare-associated infections caused by bacteria. They may affect wounds, skin, surgical sites, urinary tract, catheters, ventilators, etc. Examples include

• Clostridium difficile.

• E.coli.

• Hepatitis.

• Human immunodeficiency virus.

• Influenza.

• Klebsiella.

• Tuberculosis.

• MRSA (methicillin-resistant staphylococcus aureus).

Puncture Wounds:

A wound caused by an object piercing the skin and creating a hole is a puncture wound. They can be profound, do not result in excess bleeding, and tend to close spontaneously. A puncture wound caused by stepping on a nail becomes infected, and treatment is needed to prevent tetanus or other infections.

Bites:

Animal bites such as dog and cat bites cause tissue injury followed by infection. They are polymicrobial bacterial infections (staphylococci and anaerobes). Bites from domestic and wild animals that are not immunized increase the risk of rabies commonly are found in skunks, bats, foxes, and raccoons. Dogs, cats, rabbits, squirrels, and rodents also carry rabies. Treatment of bites includes debridement and antimicrobial therapy.

Food Poisoning:

Food poisoning is common in areas with poor hygiene. It is prevented by–

• Washing hands before cooking or eating food, after using the bathroom, changing nappies, or after contact with pets.

• Cooking meat, fish, and poultry thoroughly using a thermometer.

• Preventing cross-contamination of food in preparation areas by washing hands, cutting boards, working tops, and utensils.

Viral Infections:

Viral infections are transmitted through saliva and other body fluids in which hygiene is low and close contact with other persons or their secretions results in infections. A few examples include

• Measles.

• Rashes.

• Hepatitis.

• Human immunodeficiency virus.

• Mumps.

• Papillomavirus.

• Rabies.

• Rubella.

• Severe acute respiratory syndrome (SARS).

Hand-Foot-Mouth Disease:

Hand-foot-mouth disease is a viral infection caused by picornaviruses (coxsackie A and enterovirus 71). The clinical features are mouth ulcers, mild fever, malaise, anorexia, and rash.

What Is an Infestation?

An infestation is caused by parasites that obtain their nutrients from hosts and live on humans. Infestations are caused by parasites, mites, pests, lice, and ticks transmitted between humans, especially in poor sanitation, close contact, and war areas.

Infestations are endemic in the tropical and developing worlds and are seen frequently in developed countries, among travelers or immigrants. They are acquired from water or improperly handled food and animals (zoonotic parasites). Examples of parasitic infestation include:

• Amoebiasis: Which is common in developing countries and causes gastrointestinal disease.

• Giardiasis: Common worldwide; causes gastrointestinal disease.

• Leishmaniasis: Common in tropical and Mediterranean; causes skin lesions.

• Malaria is one of the most serious infestations worldwide, common in tropical regions where anopheline mosquitoes survive; it causes hemolysis.

• Toxoplasmosis is another serious infestation globally, endemic in developing countries; it causes eye and CNS disease.

• Worms, fleas, lice, ticks, mites, and maggots are other organisms that cause infestations.

What Are the Clinical Features of Infestation?

Clinical features include:

• Worms: Worm cysticerci are developed in the brain and eye, striated muscles in the tongue, neck and trunk, skin, and subcutaneous tissue. It is commonly caused by improper cooking of meat, pork.

• Echinococcosis: Caused by improper hand-washing and ingestion of contaminated water or food such as lamb or mutton containing eggs or cysts. This infestation does not have specific clinical signs but can become large enough to occupy space leading to compression of adjacent structures such as the liver.

• Mites: Scabies is a common infestation with mite Sarcoptes scabiei, transmitted by close contact, especially in bed. The mite burrows into superficial skin and lays eggs, resulting in an inflammatory response and an itchy rash on the wrists and interdigital.

• Maggots: Myiasis is a common condition when fly maggots invade living tissue, especially the nose, intestine, or other body parts, and feed on the host’s organs. It is common in tropical areas.

• Head lice are parasitic insects on people's heads, eyebrows, and eyelashes. They feed on human blood, live close to the scalp, and do not spread disease. Signs and symptoms include- a tickling sensation, itching, irritability and difficulty sleeping, and sores on the head caused by itching.

• Intestinal worm infestation is a global health problem caused by soil-transmitted helminth and occurs in poverty and poor sanitation communities. It is a global cause of morbidity for over two billion people in more than 100 countries.

Conclusion:

Infections are caused by microbial invasion into the body, whereas infestation is caused by parasites living on or in the body. Infection and infestation involve various organisms presenting with different signs and symptoms. Treatments include antibiotics, antifungal, antiviral, anthelminthic, and other medications. In case of abscess formation, pus drainage is done. The recommended preventive measures help reduce the risk of infections and infestations.