We refer to the intentional hosting of helminths as a therapy, but it is more than this. Evolution has determined that having a helminth-rich biota is the default state for humans, and it is already clear that there are many benefits to be gained from hosting helminths throughout life, even for people in apparently good health.
This approach views helminths as being more like vitamins, and their absence as a helminth deficiency. Almost all who are living in industrialised countries today are helminth-deficient.
Since helminths are very effective in reducing inflammation, maintaining a small colony of helminths could potentially help to prevent a whole slew of degenerative diseases and other conditions related to the silent, chronic, low-grade, systemic inflammation that exacts a relentless toll on our tissues.  
There is mounting evidence to support this view, as can be seen from the following papers and articles.
Potentially reducible health risks
Ageing / aging
Hosting helminths could be key to living longer with greater freedom from chronic disease.
- Gross ways to live long: Parasitic worms as an anti-inflammaging therapy -- Full text (Also reported by EurekAlert. )
The following study was the first of its kind to report that weekly administration of the helminth-derived product, ES-62, improved late-life health and increased lifespan (+12%, median lifespan) in a mouse model of high-calorie diet-accelerated aging. This suggests that the anti-inflammatory effects of helminthic therapy can exert protective effects even in later life.
- The parasitic worm product ES-62 promotes health- and life-span in a high calorie diet-accelerated mouse model of ageing -- Full text
- Reconstitution of the human biome as the most reasonable solution for epidemics of allergic and autoimmune diseases
- Mechanisms of tolerance and potential therapeutic interventions in Alopecia Areata -- Full text | PDF (See section 4: Gut microbiota and helminths, autoimmunity and tolerance.)
- Scientists Say Alzheimer’s Is an Autoimmune Disease, Not Result of Amyloid Plaques
- For Alzheimer’s Sufferers, Brain Inflammation Ignites a Neuron-Killing “Forest Fire”
- Apolipoprotein E4 is associated with improved cognitive function in Amazonian forager-horticulturalists with a high parasite burden -- Full text
- We present evidence that the E4 allele, often associated with cognitive decline, AD, and CVD in industrialized populations with minimal parasite burden, was associated with higher cognitive function among Tsimane Amerindians, but only among individuals with evidence of high parasite burden.
- Inhibition Effects of Nippostrongylus brasiliensis and Its Derivatives against Atherosclerosis in ApoE-/- Mice through Anti-Inflammatory Response -- Full text
- Are intestinal worms nature's anti-atherosclerosis vaccine? -- Full text | PDF
- Filarial extract of Litomosoides sigmodontis induces a type 2 immune response and attenuates plaque development in hyperlipidemic ApoE-knockout mice
- Chronic Opisthorchis felineus infection attenuates atherosclerosis--an autopsy study
- An anti-atherogenic effect of Schistosoma mansoni infections in mice associated with a parasite-induced lowering of blood total cholesterol
Chronic helminth infection may protect against atherosclerosis development via induction of anti-inflammatory responses and alteration of atherogenic biomarkers.
- Reconstitution of the human biome as the most reasonable solution for epidemics of allergic and autoimmune diseases
The following paper reveals that exposure to stress might lead to the development of autoimmune disease, and it could be argued that the powerful anti-inflammatory effects of helminths might help to interrupt this progression and reduce the risk of someone with a stress-related disorder going on to develop autoimmunity.
When a mother's immune system is modulated by helminths during pregnancy, her children will likely have a reduced risk of developing autism.
- Is Autism a Member of a Family of Diseases Resulting from Genetic/Cultural Mismatches? Implications for Treatment and Prevention
- A model for the induction of autism in the ecosystem of the human body: the anatomy of a modern pandemic?
- Microbiome Research in Autism Spectrum Disorders (Video - Helminths mentioned from 34 minutes.)
Bone healing ability, loss of in the elderly
Age-associated inflammation is responsible for the decline in the number and function of the skeletal stem cells that enable bones to heal.
- Many helminths produce excretory-secretory products with antitumor properties.  
- Parasites as negative regulators of cancer -- Full text | PDF
- The bifacial role of helminths in cancer: involvement of immune and non-immune mechanisms
- … specific pathogens may be able to elicit anti-tumor immune responses that can lead to protection from tumorigenesis or cancer regression.
- Extraintestinal helminth infection reduces the development of colitis-associated tumorigenesis -- Full text | PDF
- Helminth-derived molecules inhibit colitis-associated colon cancer development through NF-kB and STAT3 regulation
- Hookworm exposure decreases human papillomavirus uptake and cervical cancer cell migration through systemic regulation of epithelial-mesenchymal transition marker expression -- Full text | PDF
- Chronic Inflammation Linked to High-Grade Prostate Cancer
- Inflammation and cancer: how hot is the link?
- Review series on helminths, immune modulation and the hygiene hypothesis: The broader implications of the hygiene hypothesis -- Full text | PDF
Also see Helminthic therapy and cancer.
Nearly half of all adult Americans have cardiovascular disease. 
Immunotherapies that treat inflammatory conditions might have a role in the reduction of cardiovascular disease risks,  and anti-inflammatory medication allows patients with a history of heart attacks to enjoy a significantly lower incidence of recurrent cardiovascular events,  but these drugs may only be necessary because of the helminth deficiency that is widespread throughout the developed world in the twenty first century.
- Life lessons from the native tribe with the healthiest hearts in the world - Dr. Sanjay Gupta, CNN
- … it is possible that the parasites in the bodies of the Tsimane help regulate their immune systems and protect their hearts.
- Can worms defend our hearts? Chronic helminthic infections may attenuate the development of cardiovascular diseases
- … multiple lines of evidence support the notion that there is also an inverse relationship between helminthic infections and atherosclerosis and its related diseases. It is hereby hypothesized that worms are ‘protective’ against heart disease.
- Cardiovascular disease and type 2 diabetes in evolutionary perspective: a critical role for helminths? -- Full text | PDF
- Chronic infections, especially helminths, may offer protection against heart disease and diabetes through direct and indirect pathways.
- Effects of helminths and anthelmintic treatment on cardiometabolic diseases and risk factors: A systematic review -- Full text | PDF
- This rigorous, comprehensive systematic review has revealed that individuals who are hosting helminths enjoy less dyslipidemia (unhealthy levels of fats in the blood), less metabolic syndrome, less diabetes, and less atherosclerotic cardiovascular disease.
- Its authors warn that, if individuals who are at moderate or high risk for cardiometabolic disease are deprived of their helminths as a result of de-worming campaigns, they may require an increase in preventive medical care to compensate for the loss of beneficial helminth-derived immune modulation.
Chronic Obstructive Pulmonary Disease (COPD)
COPD is a group of diseases that cause airflow blockage and breathing-related problems, including emphysema and chronic bronchitis.
- Autoimmunity plays role in development of COPD
- A Phenome-Wide Association Study Uncovers a Role for Autoimmunity in the Development of Chronic Obstructive Pulmonary Disease -- Full text
- B Cells Produce the Tissue-Protective Protein RELMa during Helminth Infection, which Inhibits IL-17 Expression and Limits Emphysema
- Infection with a human hookworm-like helminth, Nippostrongylus brasiliensis, briefly initiates the onset of emphysematous pathology, but this is quickly reversed by helminth-induced regulatory mechanisms that promote tissue repair and mitigate the emphysema.
Clostridium difficile infection
- Recent work has begun to show that a type-2 immune response, most often associated with helminth infections, allergy, and asthma, may be protective during C. difficile infection.
- Got worms? Perinatal exposure to helminths prevents persistent immune sensitization and cognitive dysfunction induced by early-life infection
Helminth infection is protective against COVID-19 and its complications.
- Gastrointestinal Helminth Infection Improves Insulin Sensitivity, Decreases Systemic Inflammation, and Alters the Composition of Gut Microbiota in Distinct Mouse Models of Type 2 Diabetes -- Full text | PDF
- Our findings indicate that carefully controlled therapeutic hookworm infection in humans could be a novel approach for treating metabolic syndrome and thereby preventing T2D.
- Abundant evidence indicates that helminths and their by-products can exert immunomodulatory effects that prevent or delay the onset of T1D.… In the future, helminth-derived supplements may be included as part of a modern balanced diet.
- Helminth infections… may be protective against the development of diabetes, and this finding opens up new territory for discovery of novel therapeutics for the prevention and treatment of diabetes.
- … methods designed to suppress excess production of pro-inflammatory cytokines may form a new approach to prevent both type 1 and type 2 diabetes mellitus.
- Inhibition of autoimmune type 1 diabetes by gastrointestinal helminth infection -- Full text | PDF
- Does Strongyloides stercoralis infection protect against type 2 diabetes in humans? Evidence from Australian Aboriginal adults
- Taenia crassiceps Antigens Control Experimental Type 1 Diabetes by Inducing Alternatively Activated Macrophages -- Full text | PDF
Also see Helminthic therapy and diabetes.
Encephalitis, or brain inflammation, causes fever, confusion, memory loss, psychosis and seizures. It can progress quickly over weeks or even days and may become life-threatening.
Whether this condition is caused by infection or autoimmunity, a helminth deficiency will arguably increase the risks, whereas helminth exposure may reduce them.
Fibromyalgia has been linked to increased systemic inflammation and neuro-inflammation.
- Evidence of both systemic inflammation and neuroinflammation in fibromyalgia patients, as assessed by a multiplex protein panel applied to the cerebrospinal fluid and to plasma — Full text | PDF
Graves’ hyperthyroidism may be prevented by helminth infection or with the application of helminth-derived products.
- TSH receptor-adenovirus-induced Graves' hyperthyroidism is attenuated in both interferon-gamma and interleukin-4 knockout mice; implications for the Th1/Th2 paradigm -- Full text | PDF
Helicobacter pylori infection
Hosting helminths may provide a buffering mechanism against the harmful effects of H. pylori infection, alleviating the Th1-dependent response and protecting against inflammation within the gastrointestinal tract.
- Frequency and immunological consequences of Helicobacter pylori and intestinal parasite co-infections: a brief review
- Concurrent enteric helminth infection modulates inflammation and gastric immune responses and reduces helicobacter-induced gastric atrophy
- Intestinal helminthiasis in Colombian children promotes a Th2 response to Helicobacter pylori: possible implications for gastric carcinogenesis
Heavy metal accumulation
Some helminth species may be able to remediate heavy metal accumulation in their hosts’ tissues.
- Role of Parasitic Helminths in Bioremediating Some Heavy Metal Accumulation in the Tissues of Lethrinus mahsena
Helminth infections can reduce the susceptibility of T-cells to HIV-1 infection, so may be beneficial against HIV-1.
- Schistosoma mansoni soluble egg antigen (SEA) and recombinant Omega-1 modulate induced CD4+ T-lymphocyte responses and HIV-1 infection in vitro -- Full text
Hyperemesis gravidarum (HG) is a pregnancy complication characterised by severe nausea, vomiting, weight loss, and possibly dehydration,  which is considered more severe than morning sickness.  In view of the fact that allergy is the most significant condition associated with HG prior to pregnancy  - which suggests a possible allergic or autoimmune component - it is possible that women who are hosting helminths might be less likely to develop HG.
- Evolutionary biology and anthropology suggest biome reconstitution as a necessary approach toward dealing with immune disorders
Inflammatory bowel disease (IBD)
Helminth exposure may prevent IBD.
- Failure to acquire helminths in early life negatively affects immune development, leading to immunological diseases such as IBD later in life
- Young mice expel the tapeworm Hymenolepis diminuta and are protected from colitis by triggering a memory response with worm antigen -- PDF
Helminth infections are associated with lower insulin resistance.
- Effect of Anthelmintic Treatment on Insulin Resistance: A Cluster-Randomized, Placebo-Controlled Trial in Indonesia
Joint replacement, failure of
Helminths could extend the life of joint replacements by reducing inflammation-related bone loss.
A worm-derived immunomodulator protects against kidney damage in SLE.
- The parasitic worm product ES-62 targets myeloid differentiation factor 88-dependent effector mechanisms to suppress antinuclear antibody production and proteinuria in MRL/lpr mice -- Full text | PDF
Leg ulcers, recalcitrant
Research has identified a connection between wounds that don't heal and autoimmunity, suggesting that preventing autoimmune disease by hosting helminths might also help to reduce the risk of recalcitrant leg ulcers.
Helminth colonisation may promote longevity.
- Inflammation, not telomere length, predicts healthy longevity of centenarians
- Scientists May Have Isolated The Secret To Staying Healthy Past Age 100
- Does the trained immune system play an important role in the extreme longevity that is seen in the Sardinian blue zone? -- Full text | PDF
- NIH study suggests immune system could play a central role in AMD
- Autoimmunity in retinal degeneration: autoimmune retinopathy and age-related macular degeneration
Children with helminths may be less likely to contract malaria.
- Early helminth infections are inversely related to anemia, malnutrition, and malaria and are not associated with inflammation in 6- to 23-month-old Zanzibari children | PDF
Infection by Trichuris trichiura has been associated with direct reductions in cerebral malaria risk.
- Disentangling complex parasite interactions: Protection against cerebral malaria by one helminth species is jeopardized by co-infection with another -- Full text | PDF
Removal of helminths can increase the risk from infectious agents such as malaria and influenza.
- Review series on helminths, immune modulation and the hygiene hypothesis: immunity against helminths and immunological phenomena in modern human populations: coevolutionary legacies? -- Full text | PDF
Hosting hookworms concurrently with one species of malaria can reduce the malaria burden by almost 50 percent.
- Competing for blood: the ecology of parasite resource competition in human malaria-helminth co-infections
Helminth infection may provide protection against metabolic syndrome.
- The interplay of type 2 immunity, helminth infection and the microbiota in regulating metabolism -- Full text | PDF
Many women who suffer recurrent miscarriages exhibit autoimmune phenomena similar to what is seen in patients with Systemic Lupus Erythematosus (SLE), and these women may be treated with prednisone to reduce inflammation.
- Miscarriages can be Prevented
- Insights into causes of miscarriages for some women revealed by mice study
Also see Helminthic therapy and pregnancy.
Mold (mould) health issues
Helminthic therapy might prevent symptoms arising from mold exposure.
- Preliminary research identifies helminthic therapy as a possible treatment strategy to arrest the chronic inflammatory response, induced by mold and other biotoxins.
Muscle mass loss in the elderly
Age-related decline in muscle function may be driven by chronic inflammation.
- Mechanistic Links Underlying the Impact of C-Reactive Protein on Muscle Mass in Elderly -- Full text | PDF
Also see Helminthic therapy and narcolepsy.
Exposure to helminths may have a profoundly positive affect on neuropsychiatric disorders.   HDCs are already being used effectively as a therapeutic agent to relieve a wide range of these disorders,  (PDF)   and Bilbo and colleagues have used a laboratory model to show that colonization with H. diminuta protects rats from inflammation-induced cognitive dysfunction. 
Non-alcoholic fatty liver disease (NAFLD)
- Helminth infection and helminth-derived products: A novel therapeutic option for non-alcoholic fatty liver disease -- Full text | PDF
- … helminths and their products can treat or relieve non-alcoholic fatty liver disease (NAFLD)-related diseases, including obesity, diabetes, and metabolic syndrome, by promoting glycolipid metabolism homeostasis, regulating inflammation and restoring the balance of gut microbiota.
The results from this study suggest that helminth infection protects against obesity by altering the gut microbiota.
- Helminth-induced and Th2-dependent Alterations of the Gut Microbiota Attenuate Obesity Caused by High Fat Diet — PDF
Helminths prevented weight gain in laboratory mice on a high-fat diet. They did this by boosting populations of bacteria that produce compounds which trigger increased energy consumption.
This paper reports that a helminth infection can be associated with improved lipid profile in overweight/obese individuals, a feature that might contribute to reducing the risk of cardiometabolic diseases in this population.
- Schistosoma haematobium infection is associated with lower serum cholesterol levels and improved lipid profile in overweight/obese individuals
Obsessive-compulsive disorder (OCD)
Obstructive sleep apnea
- Osteoarthritis as an inflammatory disease (osteoarthritis is not osteoarthrosis!) -- Full text | PDF
- … initially considered cartilage driven, OA is a much more complex disease with inflammatory mediators released by cartilage, bone and synovium. Low-grade inflammation induced by the metabolic syndrome, innate immunity and inflammaging are some of the more recent arguments in favor of the inflammatory theory of OA…”
Chronic inflammation may cause neurodegeneration in Parkinson's disease.
Parkinson's disease may originate in the intestines.
- Evidence for bidirectional and trans-synaptic parasympathetic and sympathetic propagation of alpha-synuclein in rats
The use of immunosuppressant drugs may keep Parkinson's disease at bay, and may also slow progression of the disease if it develops.
- Drugs that suppress immune system may protect against Parkinson’s
- Oxidative Stress, Pro-Inflammatory Cytokines, and Antioxidants Regulate Expression Levels of MicroRNAs in Parkinson's Disease
Helminths can achieve similar beneficial effects to immunosuppressants without the long term adverse side effects.
- Better regulation of the immune system may minimize preeclampsia symptoms
- Is preeclampsia an autoimmune disease? (Full text)
- Autoimmune Genes Linked To Preeclampsia
Also see Helminthic therapy and pregnancy.
- (Science Alert have published a very readable article about this research.)
- Some psychosis cases an 'immune disorder'
- Psychosis: an autoimmune disease?
- A clinical approach to new-onset psychosis associated with immune dysregulation: the concept of autoimmune psychosis
Restless Legs Syndrome (RLS)
RLS has been associated with inflammation.
- Circulating levels of cytokines are increased in restless legs syndrome
- Severe recurrent restless legs syndrome associated with systemic inflammation
- Association between the neutrophil-to-lymphocyte ratio, a new marker of systemic inflammation, and restless legs syndrome -- Full text | PDF
- Restless legs syndrome - Theoretical roles of inflammatory and immune mechanisms -- PDF
Rheumatoid arthritis (RA)
- Protection Against Arthritis by the Parasitic Worm Product ES-62, and Its Drug-Like Small Molecule Analogues, Is Associated With Inhibition of Osteoclastogenesis -- Full text | PDF
The risk for rosacea, as well as other skin disorders such as atopic eczema and onychomycosis (toenail fungus), increase with the presence of systemic low-grade inflammation.
- What's The Connection Between Schizophrenia and Autoimmune Diseases?
- Inflammation and Schizophrenia, YouTube
- Immune clue to preventing schizophrenia
- Microglial Activity in People at Ultra High Risk of Psychosis and in Schizophrenia: An (11C)PBR28 PET Brain Imaging Study (PDF)
- Reducing Inflammation May Improve Cognition in Schizophrenia
- Helminths and their implication in sepsis - a new branch of their immunomodulatory behaviour? -- Full text | PDF
- Chronic Filarial Infection Provides Protection against Bacterial Sepsis by Functionally Reprogramming Macrophages -- Full text | PDF
- Fh15 Blocks the Lipopolysaccharide-Induced Cytokine Storm While Modulating Peritoneal Macrophage Migration and CD38 Expression within Spleen Macrophages in a Mouse Model of Septic Shock — Full text | PDF
- A helminth-derived molecule significantly suppressed the inflammation-driven cytokine storm in a mouse model of septic shock.
- Fasciola hepatica GST downregulates NF-κB pathway effectors and inflammatory cytokines while promoting survival in a mouse septic shock model -- Full text | PDF
- Young people with chronic illness more likely to attempt suicide
- Allergy: A Risk Factor for Suicide?
Systemic lupus erythematosus (SLE)
Infection with the murine helminth, Hymenolepis microstoma (HM), protected mice against the development of lupus, improved all signs and symptoms of the disease, and prevented death.
Venous thromboembolism (VTE)
(Also pulmonary embolism (PE) and deep vein thrombosis (DVT)).
Inflammation appears to change the hemostatic balance towards thrombogenesis, and autoimmune disorders have been linked to an increased risk of VTE.
Testimonies to health enhancement
Well people who host helminths as prophylaxis against autoimmune and inflammation-related conditions may never know exactly how much their worms have helped to keep them well but, occasionally, a case is reported that hints at the extent of the potential benefits.
When a clinical pathologist specialising in medical microbiology heard about helminthic therapy, he decided he had to experience what was involved, but he had no expectation of benefit beyond hoping that it might possibly improve his seasonal hay fever. In the event, he experienced several additional benefits.