A parasitic disease is an infectious condition that occurs secondarily to invasion of a plant or animal, which uses the body in a way, that is beneficial to the parasite but not the body. There are numerous types of parasites that may invade the body causing a variety of diseases and conditions. The rating schedule represents some of the most widespread parasitic diseases encountered by veterans in various venues. Those conditions not specified by the rating schedule should be investigated in accordance with the specific causative parasite.

Etiology

While most parasitic diseases have a known or reasonably suspected etiology (the parasite responsible and its mode of transmission), some cases or conditions might fall under the broad category of "otherwise unspecified etiology" due to several factors: 

• Emerging or Novel Parasites: New parasites are constantly being discovered or identified as causing illness, and their full life cycles and modes of transmission might not be immediately understood.
• Complex or Multifactorial Cases: In some instances, multiple parasites might be present, or the symptoms could be caused by a combination of factors, making it challenging to pinpoint a single causative agent.
• Limitations of Diagnostic Tools: Current diagnostic methods might not be sensitive or specific enough to detect all parasites, especially rare or emerging ones, or when the parasite burden is low.
• Geographical or Environmental Factors: Certain parasites might thrive in specific ecological niches, and if a patient travels to or resides in such an area, it can be challenging to determine the exact parasite without specific knowledge of the local epidemiology.
• "Neglected" or Understudied Parasites: Some parasitic infections are considered "neglected" and receive less attention and research, leading to gaps in knowledge about their etiology and treatment options. 

Signs & Symptoms

Parasitic infections can cause a variety of symptoms, depending on the specific parasite involved and the body systems it affects. Some individuals may even be asymptomatic. 

However, some common signs and symptoms associated with parasitic infections include: 

Gastrointestinal issues

• Diarrhea
• Abdominal pain and cramps
• Gas and bloating
• Nausea and vomiting 

Other symptoms

• Fatigue and weakness
• Unexplained weight loss or increased appetite
• Skin rashes and itching
• Muscle aches and joint pain
• Fever and chills
• Insomnia or difficulty sleeping
• Anemia or iron deficiency 

Tests

1. Stool analysis

• Ova and Parasite (O&P) Test: This is a common and initial test for detecting parasites in the gastrointestinal tract. Multiple stool samples collected on separate days are recommended by the Centers for Disease Control and Prevention | CDC. The samples are examined under a microscope to identify parasitic eggs (ova), larvae, cysts, or adult parasites.
• Special Stains and Tests: Healthcare providers might request special stains or additional tests to identify parasites not routinely screened for.
• Molecular Diagnosis (PCR): When microscopic identification is difficult, especially with low parasite counts in stool samples, molecular techniques like Polymerase Chain Reaction (PCR) may be used to identify parasitic DNA. 

2. Blood tests

• Serology: This test detects antibodies produced by the immune system in response to a specific parasitic infection, or antigens released by the parasite itself.
• Blood Smear: This test involves examining a blood smear under a microscope to identify parasites living in the blood, such as those causing filariasis, malaria, or babesiosis.
• Other Blood Tests: Complete Blood Count (CBC) and Chemistry Panel (CMP) can provide valuable information about anemia, deficiencies, and organ involvement, which might be linked to parasitic infections. 

3. Endoscopy/colonoscopy

• These procedures involve inserting a tube with a camera into the digestive tract to visually examine the intestines for parasites or other abnormalities when stool exams are inconclusive. 

4. Imaging tests

• X-ray, MRI, CT Scans: These imaging techniques are used to detect some parasitic diseases that may cause lesions or damage within organs. 

5. Other tests

• Biopsy: Tissue samples from lesions or suspected infected organs can be biopsied and examined microscopically for the presence of parasites.
• Skin Snip: For specific parasites like Onchocerca volvulus, skin snips may be taken to detect microfilariae. 

Treatment

Treating parasitic infections generally involves a combination of medication and supportive care, according to the Cleveland Clinic. The specific medications and approaches depend on the type of parasite, the severity of the infection, and the patient's individual health status. 

1. Antiparasitic medications

• Anthelmintics: These drugs target and eliminate parasitic worms (helminths) like roundworms, hookworms, and tapeworms. Examples include:
  • Albendazole: Effective against various worms.
  • Mebendazole: Used for threadworm, roundworm, and whipworm infections.
  • Praziquantel: Effective against tapeworms and schistosomiasis.
  • Ivermectin: Treats roundworm infections and certain types of mites, like scabies.
• Antiprotozoal medications: These drugs treat infections caused by protozoa, including amoebiasis, giardiasis, and malaria. Examples include:
  • Metronidazole: Used for amoebiasis, giardiasis, and trichomoniasis.
  • Chloroquine: Treats and prevents malaria.
  • Atovaquone: Treats Pneumocystis jirovecii pneumonia and prevents Plasmodium falciparum malaria.
  • Tinidazole: Also effective against trichomoniasis, giardiasis, and amoebiasis. 

2. Supportive care

In addition to medication, supportive care measures are often crucial to manage symptoms, support recovery, and prevent complications. These include: 

• Hydration: Especially important in cases of diarrhea and vomiting to prevent dehydration.
• Nutritional Support: Ensuring adequate nutrition with a balanced diet can support the immune system and aid recovery, according to the Cleveland Clinic.
• Rest: Allows the body to conserve energy and recover.
• Pain Relief: Over-the-counter pain relievers like ibuprofen or acetaminophen may be used to manage pain and fever. 

3. Prevention and lifestyle modifications

Preventing parasitic infections is crucial to avoid recurrence and control spread. 

• Good Hygiene: Frequent handwashing with soap and water, especially after using the bathroom, is essential.
• Safe Food and Water: Avoid consuming undercooked meat or fish and untreated water sources.
• Insect Protection: Using insect repellent and protective clothing can help prevent insect-borne parasitic infections.
• Sanitation: Proper sewage treatment and maintaining clean environments can help prevent transmission. 

Residuals

Parasitic infections can lead to various long-term effects and residual disabilities, even after the initial infection has cleared or been treated. These are sometimes referred to as sequelae of parasitic diseases. The specific residuals depend on the type of parasite, the severity and duration of the infection, and individual factors like immune status. 

Neurological residuals

• Neuroinflammation and brain damage: Some parasites can invade the central nervous system (CNS) or trigger neuroinflammation, leading to conditions like encephalitis, meningitis, or abscesses.
• Seizures and Epilepsy: Neurocysticercosis and cerebral malaria, among other parasitic infections affecting the brain, can cause seizures or epilepsy.
• Cognitive and Behavioral Changes: Chronic parasitic infections can affect brain function, potentially leading to cognitive impairment, behavioral disorders, headaches, and personality shifts.
• Other Neurological Symptoms: Focal neurological deficits, increased intracranial pressure, and problems with vision or motor function can also arise. 

Gastrointestinal residuals

• Chronic Gastrointestinal Issues: Parasites can disrupt the gut lining and lead to lasting digestive problems such as diarrhea, constipation, bloating, nausea, and abdominal pain.
• Malabsorption and Nutritional Deficiencies: Parasites can interfere with the body's ability to absorb nutrients, potentially leading to malnutrition, anemia (including iron-deficiency anemia), and deficiencies in essential vitamins like B12.
• Increased Risk of Other Infections: Intestinal damage from parasitic infections can make individuals more susceptible to other infections. 

Other potential residuals

• Chronic Fatigue Syndrome (CFS): Parasitic infections, particularly Giardiasis, are associated with chronic fatigue syndrome and its accompanying symptoms like fatigue, exhaustion, brain fog, and muscle aches.
• Musculoskeletal Problems: Parasites can invade joint spaces and muscles, potentially causing arthritis, joint pain, and inflammation.
• Cardiac Problems: Certain parasites can affect the heart, causing myocarditis, pericarditis, or contributing to heart failure.
• Skin Issues: Parasitic infections can lead to chronic skin irritation, rashes, hives, or eczema.
• Organ Damage: In some cases, migrating parasites or inflammatory responses to their presence can cause damage to organs like the liver, lungs, or eyes. 

1. This disease shall be granted service connection although not otherwise established as incurred in or aggravated by service if manifested to a compensable degree within the applicable time limits under §3.307 following service in a period of war or following peacetime service on or after January 1, 1947, provided the rebuttable presumption provisions of §3.307 are also satisfied [38 CFR 3.309 [Disease subject to presumptive service connection], §3.309(a) [chronic disease].

2. May be entitled to special monthly compensation where the veteran has a single service-connected disability rated as 100% and/or other requirements/qualifications under 38 CFR §3.350 [Special monthly compensation ratings]. Also reference 38 CFR 3.155(d)(2).

3. This disease shall be granted service connection as a result of tropical service, although not otherwise established as incurred in service if manifested to a compensable degree within the applicable time limits under §3.307 or §3.308 following service in a period of war or following peacetime service provided the rebuttable presumption provisions of §3.307 are also satisfied [38 CFR 3.309 (b) Disease subject to presumptive service connection].

1. As active disease rate as 100%, thereafter, rate under the appropriate body system any residual disability of infection.