Multiple sclerosis in the Orkney and Shetland Islands. II: The search for an exogenous aetiology

The risk of multiple sclerosis on the Orkney islands. A review of the search for distinctively Orcadian risks, with a hypothesis for further investigations

The most extensive and meticulous epidemiological study yet to be published on the frequency of multiple sclerosis (MS) across the regions of Scotland has confirmed that the high incidence of MS on the Orcadian islands is unique and is most probably the highest in the world. Environmental and genetic studies of Orcadian MS have been carried out over many years but the results have been discouragingly inconclusive; no convincing explanation of the distinctively high Orcadian MS risks has come to light. However, studies of both prevalence and incidence of MS over a time line of approximately five decades, show that Orcadian MS has steadily increased to significantly exceed the neighbouring genetically related populations including North Eastern Scotland and the Shetland islands. Over this period the islands have progressively expanded occupations related to agriculture and have simultaneously acquired the highest concentration of cattle in Europe. Coinciding high and increasing Orcadian MS risk with increasing agricultural activities including bovine density and dairying, points towards a potential but unexpected causal risk. Raised incidence of MS with farming and in particular with dairy farming have been documented in Australia, Denmark, and more recently in Norway, further pointing to a possible MS risk associated with agricultural activities. A clue to the cause of this curious association has unexpectedly emerged from laboratory studies. Using very rarely available tissues from patients coming to autopsy during an MS attack, a toxin known as beta-haemolysin (sphingomyelinase), which is produced by the bacterium Staphylococcus aureus, has been identified in the affected tissues. Staph aureus is a common inhabitant of the mucosal linings of the human nasal sinuses and sinus mucosal inflammations have been shown to be closely associated with attacks of MS and optic neuritis. Irrespective of origin, human or animal, all strains of Staph aureus carry the beta haemolysin gene. However, the toxin is only sporadically expressed by the strains most commonly isolated from human carriers. Strains carried by bovines nearly always express toxin. Has the increasing high risk of MS in Orcadians been promoted by the nasal transmission and subsequent establishment of the high secreting bovine genotypes of Staph aureus in the Orcadian population? To demonstrate that bovine associated strains of Staph aureus are carried more frequently in the Orcadian population (or even specifically in Orcadian MS cases), would not of itself necessarily explain the high prevalence of Orcadian MS. It would however clearly justify an in-depth exploration of the nasal bacterial microbiome of MS cases. This should include the incidence of beta-toxin secreting Staph aureus genotypes. If MS cases are shown to have a distinctive nasal bacterial microbiome, including beta-toxin secretors, this finding would open up an almost entirely new range of investigations and approaches to the understanding of the pathogenesis of MS.

Environmental Factors and Their Regulation of Immunity in Multiple Sclerosis

In multiple sclerosis (MS), environmental factors and genetic traits cooperate in the induction of the chronic activation of immune cells to produce the brain pathology. Epidemiology has focused on different environmental risk factors but certainly virus infection, smoking, vitamin D levels, and sunlight exposure are the most relevant. What is certainly less clear is the way in which these external factors are able to induce and sustain the internal pathology process of the disease. Epigenetics has been recently focused on trying to shed light on this aspect. As a matter of fact epigenetic changes are highly sensitive to environmental factors that therefore may influence the susceptibility to the disease by acting through epigenetic modifications. In this chapter we discuss the most relevant environmental factors and how they may affect the immune response in MS. Finally, we discuss the possible role of the microbiota in inducing autoimmunity in MS.

Socioeconomic factors in childhood and the risk of multiple sclerosis

In a national cohort comprising 1.5 million Danes born from 1966 to 1992, we studied the association between childhood socioeconomic status (SES) and the risk of multiple sclerosis (MS) from 1981 to 2007 using information about household income and parental educational levels at the person's 15th birthday. The association between childhood SES and MS was evaluated using MS incidence rate ratios with 95% confidence intervals obtained in log-linear Poisson regression analyses. We found no strong association between childhood SES and MS but did observe a tendency toward a reduced risk of MS among children from households with more highly educated parents, particularly mothers. Children whose mothers had a secondary (rate ratio = 0.95, 95% confidence interval: 0.86, 1.04) or higher (rate ratio = 0.86, 95% confidence interval: 0.76, 0.97) education had reduced risks of MS (5% and 14%, respectively) compared with children of mothers with a basic education (P for trend = 0.02). Results were practically unchanged in an analysis restricted to persons aged 15-29 years, among whom the possible effect of own SES on MS risk is considered limited. Overall, SES in childhood seems of no major importance for the subsequent risk of MS; however, offspring of well-educated mothers may be at a slightly reduced risk of MS.

Surgery and risk for multiple sclerosis: a systematic review and meta-analysis of case-control studies

BACKGROUND

Although the precise etiology of multiple sclerosis is largely unknown, there is some speculation that a prior history of surgery may be associated with the subsequent risk for developing the disease. Therefore, we aimed to examine surgery as a risk factor for the diagnosis of multiple sclerosis.

METHODS

We searched for observational studies that evaluated the risk for developing multiple sclerosis after surgery that occurred in childhood (≤ 20 years of age) or "premorbid" (> 20 years of age). We specifically included surgeries classified as: tonsillectomy, appendectomy, adenoidectomy, or "surgery". We performed a systematic review and meta-analyses and calculated odds ratios (OR) and their 95% confidence intervals (CIs) using a random effects model.

RESULTS

We identified 33 case-control studies, involving 27,373 multiple sclerosis cases and 211,756 controls. There was a statistically significant association between tonsillectomy (OR = 1.32, 95% CI 1.08-1.61; 12 studies, I(2) = 44%) and appendectomy (OR = 1.16, 95% CI 1.01-1.34; 7 studies, I(2) = 0%) in individual's ≤ 20 years of age and the subsequent risk for developing multiple sclerosis. There was no statistically significant association between risk for multiple sclerosis and tonsillectomy occurring after age 20 (OR = 1.20, 95% CI 0.94-1.53; 9 studies, I(2) = 32%), in those with appendectomy at > 20 years (OR = 1.26, 95% CI 0.92-1.72; 5 studies, I(2) = 46%), and in those with adenoidectomy at ≤ 20 years of age (OR = 1.06, 95% CI 0.68-1.68; 3 studies, I(2) = 35%). The combined OR of 15 studies (N = 2,380) looking at "surgery" before multiple sclerosis diagnosis was not statistically significant (OR = 1.19, 95% CI 0.83-1.70; I(2) = 71%).

CONCLUSIONS

We found a small but statistically significant and clinically important increased risk for developing multiple sclerosis, in those with tonsillectomy and appendectomy at ≤ 20 years of age. There was no convincing evidence to support the association of other surgeries and the risk for multiple sclerosis. Well-designed prospective etiological studies, pertaining to the risk for developing multiple sclerosis, ought to be conducted and should include the examination of various surgeries as risk factors.

Environmental factors and their regulation of immunity in multiple sclerosis

Epidemiological and clinical studies have shown that environmental factors such as infections, smoking and vitamin D are associated with the risk of developing multiple sclerosis (MS). Some of these factors also play a role in the MS disease course. We are currently beginning to understand how environmental factors may impact immune function in MS on a cellular and molecular level. Here we review epidemiological, clinical and basic immunological studies on the environmental factors, viral and parasitic infections, smoking, and vitamin D and relate epidemiological findings with their likely pathophysiology in MS.

Genome-wide homozygosity and multiple sclerosis in Orkney and Shetland Islanders

There is strong evidence for both genetic and environmental risk factors comprising the aetiology of multiple sclerosis (MS). While much progress has been made in recent years in identifying common genetic variants using genome-wide association studies, alternative approaches have remained relatively neglected. The prevalence of MS in Orkney and Shetland is among the highest in the world. Previous studies have suggested that a higher degree of parental relatedness in these isolated communities may contribute to the high rates of MS, indicating that recessive effects have an important role in MS aetiology. The Northern Isles Multiple Sclerosis (NIMS) study investigated the potential role of genome-wide homozygosity in MS risk by genotyping 88 MS patients, 89 controls matched by age, sex and ancestry, and a further 89 controls matched for sex and ancestry, but passed the majority of lifetime risk of developing MS (>70 years of age). Three participants were removed on the basis of pedigree-genomic anomalies (n=263). Three measures of genome-wide homozygosity were generated for each individual, and association with MS was assessed using logistic regression models. No effect of genome-wide homozygosity was detected, indicating that inbreeding and consanguinity are not risk factors for MS in this population.

Regional, socioeconomic and occupational groups and risk of hospital admission for multiple sclerosis: a cohort study in Sweden

Objective

The aim of this study was to investigate possible associations between hospitalization for multiple sclerosis (MS) and region, socioeconomic status and occupation.

Methods

A nationwide database was constructed by linking Swedish Census data to the Hospital Discharge Register (1987–2001). The hospital diagnoses of MS were based on the International Classification of Diseases. Standardized incidence ratios (SIRs) with 95% confidence intervals were calculated.

Results

Significantly increased or decreased risks of hospitalization for MS were found for individuals living in some counties. The overall SIRs for hospitalizations for MS were close to unity between different socioeconomic groups. Male religious workers, male postal workers and female administrators who had the same occupational title in two consecutive censuses had substantially higher risks of hospitalization for MS than the reference group. However, no increased risks were found for most occupational groups.

Conclusions

The present study suggests that region, socioeconomic status and occupation have a minor effect on the population’s risk of hospitalization for MS.

Role of return migration in the emergence of multiple sclerosis in the French West Indies

The emergence of multiple sclerosis in island societies has been investigated only in a few Caucasian populations living in temperate regions. The effect of human migration on the risk of developing this disease is still an open question because of possible genetic selection. We conducted an epidemiological study of the multiple sclerosis population in the French West Indies (Martinique and Guadeloupe), a population which includes large numbers of West Indians who have returned after emigrating to metropolitan France. Standardized incidence ratios (SIRs) for multiple sclerosis among migrants were calculated and their genetic characteristics were compared to those of non-migrants. The crude prevalence of multiple sclerosis was 14.8/10(5) on December 31, 1999 (95% CI: 11.9-17.7); and its crude mean annual incidence for the period July 1, 1999 to June 30, 2002 was 1.4/10(5) (95% CI: 1.0-1.8), confirming its emergence in the French West Indies. Recurrent neuromyelitis optica, which is virtually the only form of multiple sclerosis in black African populations in tropical regions, represented not >17.8% of these cases. During the 1,440,000 person-years of follow-up, 33 incidence cases were identified in migrants. Since the number of expected cases was 19.3, the overall SIR was 1.71 (95% CI: 1.19-2.38; P < 0.01) among migrants. The increase in the SIR was more marked if the stay was made before the age of 15 years (4.05, 95% CI: 2.17-6.83; P < 0.0001). European ancestry in the two migrating and non-migrating populations was similar. Martinique, which has a higher rate of return migration, has a higher prevalence of multiple sclerosis (21.0/10(5) versus 8.5/10(5)) and a higher incidence (2.0/10(5) versus 0.7/10(5)) than Guadeloupe. The emergence of the disease in the French West Indies is of environmental rather than genetic origin. It may be explained either through the introduction by migrants of precipitating environmental factors that operate in a critical way before the age of 15 years, and/or by the recent disappearance from the French West Indies of protective environmental factors acting before this age.

Parental age, family size, and risk of multiple sclerosis

BACKGROUND

Family structure, such as having siblings, provides proxy measures for a variety of characteristics relevant to disease risk. The etiology of multiple sclerosis (MS) is not well defined and analysis of family structure may provide etiologic clues. We conducted a case-control study to examine possible associations.

METHODS

Using the Swedish Inpatient Register, we identified 4443 patients with a diagnosis of MS. From the general Swedish population, using birth and death registers, we selected 24,194 controls with similar characteristics for year, county of birth, and survival until at least age at diagnosis of the matched cases. The Multi-Generation Register linked data on siblings and parents. The Census provided father's social class based on occupation.

RESULTS

Having 3 or more younger siblings, compared with none, produced an adjusted odds ratio (OR) for MS (with 95% confidence interval) of 0.80 (0.70-0.92) (adjusting for number of siblings, twins, maternal and paternal age, parental MS, sex, father's social class, county and year of birth). With 3 or more older siblings, the adjusted OR was 0.83 (0.72-0.96). Different-sex twin pairs compared with singletons had an OR of 0.59 (0.37-0.95) for MS. The risk of MS increased steadily with father's age but not mother's age, up to 2.00 (1.35-2.96) for 51- to 55-year-old fathers (compared with 21- to 25-year-old fathers).

CONCLUSIONS

Parents who have offspring with MS may have subtly impaired fertility. The unexpected association with paternal age may be the result of an increased risk of accumulating germ cell mutations among older men.

Multiple sclerosis and nutrition

Benefits from any particular diet in multiple sclerosis (MS) have not yet been proven. It is, however, frequent that malnutrition may potentially exacerbate the symptoms of MS. There is some evidence that a high intake of saturated fat increases the incidence of MS. Epidemiological studies imply that unsaturated fatty acids may have a positive effect on the course of MS. However, the results of controlled studies are ambiguous. A meta-analysis of three small controlled clinical trials suggests a benefit from linoleic acid. Intake of Vitamin D is associated with a lower incidence of MS. In MS, the risk of osteoporosis is high, and prophylactic vitamin D and calcium should be considered at an early stage. The role of minerals, trace elements, antioxidants, vitamins or fish oil is unclear. The possible relationships between diet and MS have not been subjected to adequate study. It seems possible that in the future, diets or dietary supplements may become recommended forms of treatment for MS.

[Diet and multiple sclerosis]

Beneficial effects from any particular diet have not been proven in multiple sclerosis (MS). Therefore, the general guidelines on nutrition should be followed. Obesity and various forms of malnutrition worsening the MS symptoms are frequently observed. There is some evidence from epidemiological studies that a high consumption of saturated animal fat is associated with an increased incidence of MS. The findings from such studies indicate that supplementation with unsaturated fatty acids, in particular omega-3 fatty acids, could positively influence the course of MS. However, controlled studies did not show clear beneficial effects from polyunsaturated fatty acids. The intake of vitamin D is associated with a lower incidence of MS. In contrast, the effects of therapy with vitamin D on the course of MS have not been ascertained. Patients with MS carry an enormous risk of osteoporosis, and therefore the indication for a preventive therapy with vitamin D and calcium should be established in every postmenopausal woman or after repeated steroid treatments.

Environmental risk factors in multiple sclerosis aetiology

The epidemiology of multiple sclerosis (MS) has been intensively studied. It is conceptualised as a complex disease in which genetic and environmental factors act together to cause disease. There are temporal and geographic variations in disease risk, and risk of disease may be affected by migration between regions of differing risk. Numerous potential causal factors including infection, immunisations, physical and emotional stressors, climate, diet, and occupational exposures have been studied using various observational study designs. Thus far, no single environmental exposure has been consistently identified as a causal factor in MS, but sufficient data have accumulated that causal pathways should be postulated and tested. This review will focus on the environmental epidemiology of MS.

Multiple sclerosis in the Faroe Islands. 7. Results of a case control questionnaire with multiple controls

Detailed questionnaires were completed in 1978–79 by 23 of the 28 then known resident Faroese multiple sclerosis (MS) patients and 127 controls. These controls were divided into 69 Group A (patient sibs and other relatives), 37 Group B (matched neighbor controls, their spouses and sibs, plus patient's spouse), and 21 Group C (distant matched controls, spouses, relatives living where MS patients never resided and British troops were not encamped during the war). No differences between cases and controls were found for education, occupation, types of residence, bathing, sanitary or drinking facilities, and nature of house construction or heating. Detailed dietary histories, available for half the subjects, revealed no difference, cases versus controls, for four age periods between age 0 and 30 years, and for 16 specified foodstuffs. Animal exposures showed overall no consistent differences by location or type of animal. There was a tendency to greater exposure to British troops during the war for cases versus Groups A and B, but this did not attain statistical significance. Vaccinations for smallpox, tetanus and diphtheria were less common in the MS; no difference was found for other vaccinations. Except for a relative deficit in the cases for rubella and (insignificantly) for measles, mumps and chicken pox, reported illnesses were equally common among all groups. Operations, hospitalizations and injuries did not differentiate the groups, nor did age at menarche for women. Neurologic symptoms were significantly more common in the cases than in the controls.

Risk factors for multiple sclerosis: a case-control study in Israel

This case-control study was aimed at identifying environmental risk factors for multiple-sclerosis (MS). Ninety-three Israeli-born MS patients identified in country-wide studies and 94 age- and sex-matched controls were interviewed. The questionnaire covered a large span of factors at ages 0, 10 and onset of the disease, with particular emphasis on socioeconomic status (SES) and sanitary conditions (SAN). A significantly larger percentage of patients reported frequent respiratory educational levels than controls. The SES and SAN at age 10 were also systematically higher among patients, but significance was reached only when the frequencies of conditions indicating extremely low values of SES or SAN were compared. It is possible that the protective effect of low SES or SAN on risk of MS can be detected only when living conditions are well below average, as is frequent in developing countries.

Environmental risk factors in MS: a case-control study in Moscow

Environmental influences operating as possible risk factors in MS were studied in Moscow. The study included 155 MS patients from the Neurology Departments and the outpatient clinics of the First City Hospital of Moscow and 155 controls matched for sex, age in 5-year intervals, nationality, and origin (Moscow vs. non Moscow). 72.3% of controls were recruited among patients from the same hospital as the cases. The remaining controls were volunteers from the hospital staff or medical students. Exposures before age 15 were of special interest. MS patients reported a higher frequency of: 1) tonsillitis; 2) allergic reactions age 15; 3) head trauma below age 16; 4) a predominant meat vs. vegetable diet during childhood. Stratified analysis and logistic regression pointed to "meat predominance" as the most significant risk factor. Other associations were confounded by the respondents' occupations/education.

Is there a case for a virus aetiology in multiple sclerosis?

Multiple Sclerosis (MS) is a devastating demyelinating disease with a very high prevalence in North-East Scotland and in the Orkney and Shetland Islands. MS appears to be a multifactorial disorder with environmental and genetic elements and it has been proposed that these, in tandem, provoke an autoimmune response giving rise to the disease. Although there is no direct evidence of a specific virus being involved in MS, there are nevertheless grounds for suspecting a viral association. This review discusses these aspects of MS and suggests that a more aggressive approach to unravelling the role of viruses is needed.

Evidence for multiple sclerosis as an infectious disease

Evidence for a viral cause of multiple sclerosis (MS) is indirect since no infectious agent has been reproducibly isolated from MS tissues nor has viral genome or antigen been consistently identified. The occurrence of spontaneous human and animal models of demyelination, serologic studies, and epidemiologic data provide persuasive circumstantial evidence for an infectious trigger in this disease. Potential mechanisms for viral induced demyelination include persistent infection of host tissues or immune mediated organ damage either in the presence or absence of the infectious agent. Any proposed viral candidate should cause demyelination in animals or man and the pattern of infection should be consistent with the unique geographic features of MS epidemiology. In addition, serologic studies should support an infection by the agent and/or viral genome should be detected in MS tissues. At this time no virus can be unequivocally linked to MS but cumulative evidence is more supportive of canine distemper virus than other viruses.

Epidemiologic evidence for multiple sclerosis as an infection

The worldwide distribution of multiple sclerosis (MS) can be described within three zones of frequency: high, medium, and low. The disease has a predilection for white races and for women. Migration studies show that changing residence changes MS risk. Studies of persons moving from high- to low-risk areas indicate that in the high-risk areas, MS is acquired by about age 15. Moves from low- to high-risk areas suggest that susceptibility is limited to persons between about ages 11 and 45. MS on the Faroe Islands has occurred as four successive epidemics beginning in 1943. The disease appears to have been introduced by British troops who occupied the islands for 5 years from 1940, and it has remained geographically localized within the Faroes for half a century. What was introduced must have been an infection, called the primary MS affection (PMSA), that was spread to and from successive cohorts of Faroese. In this concept, PMSA is a single widespread systemic infectious disease (perhaps asymptomatic) that only seldom leads to clinical neurologic MS. PMSA is also characterized by a need for prolonged exposure, limited age of susceptibility, and prolonged incubation. I believe that clinical MS is the rare late outcome of a specific, but unknown, infectious disease of adolescence and young adulthood and that this infection could well be caused by a thus-far-unidentified (retro)virus.

Multiple sclerosis and delayed mumps

To test the hypothesis that mumps occurs less frequently and later in patients with multiple sclerosis, histories were taken from patients and matched controls by a single observer at a university hospital in Canada, and in the course of domiciliary visits in England. 63 consecutive patients with multiple sclerosis in two neurological practices, and 63 controls matched for age, sex and childhood domicile, together with 29 sibs of English patients were studied. Patients had mumps at an older age (12.3:8.6, p less than 0.04) and less frequently (33/63 vs 60/92, p = 0.08). Multiple sclerosis patients display a partial immunity to mumps, of which the most obvious explanation is a preceding infection by an antigenically related paramyxovirus, that is, by either the Newcastle Disease virus, or parainfluenza.

A review of the aetiology of multiple sclerosis: an ecological approach

Multiple sclerosis (MS) is a disease of unknown aetiology characterized by myelin destruction. Approaches to the aetiology of the condition have noted its differential geographic and demographic distribution; a tentative and inconsistent link with infectious agents; a genetic susceptibility; and a tendency to track with dietary lipids. This review proposes a multidisciplinary approach to the aetiology of MS, emphasizing the interlocking and interdependent nature of current aetiological arguments. We suggest that the most profitable interpretation of current empirical data on the aetiology of MS can be accomplished through this kind of analysis.

A case-control epidemiological study of MS in the Paris area with particular reference to past disease history and profession

A retrospective case-control study was carried out on 230 patients with multiple sclerosis (MS) and 230 controls matched for year of birth and sex. The geographical distribution of residence of MS patients and controls was similar. Two peak ages of onset of MS were observed among woman patients (20-24, 30-34 years). There was no difference in histories of infectious diseases and autoimmune diseases between the two groups. A greater number of hairdressers was noticed among the patient group (p less than 0.05) and three patients (no control) had had professional contact with pathology specimens.

Risk factors in multiple sclerosis: a population-based case-control study in Hautes-Pyrénées, France

A population-based study of the prevalence and risk factors of multiple sclerosis (MS) was conducted in the Hautes-Pyrénées, the southwestern region of France. The prevalence rate per 100,000 was equal to 40. Data on the past medical history of 63 MS patients and matched controls were collected. The frequency and age at occurrence of common childhood infections were similar for both the MS cases and controls. There was no difference between the frequency of vaccination for MS patients and for controls. However, the age at which MS patients were immunized against poliomyelitis was significantly higher than the corresponding age for controls (15.8 years versus 8.9 years, P less than 0.01). Antibody titers for various viruses were measured. The mumps antibody titer was significantly higher in the MS patients than in the controls. Also, MS patients tended to have higher titers for measles antibodies.

Monoclonal autoantibodies derived from multiple sclerosis patients and control persons and their reactivities with antigens of the central nervous system

Peripheral blood B lymphocytes of multiple sclerosis (MS) patients and control persons were transformed with Epstein-Barr virus. Antibody production of transformed cells against isolated human myelin was investigated by enzyme-linked immunosorbent assay (ELISA). Cells producing reactive antibodies were cloned and propagated to produce monoclonal antibodies (mAbs). These mAbs did also react with acetone fixed frozen sections of normal human white matter, as determined by indirect immunofluorescence staining. Some of the mAbs derived from MS patients and a control person with a central nervous system cyst agglutinated liposomes made from lipids of a chloroform/methanol extract of human myelin, whereas mAbs derived from four glioma patients were negative in these tests. The reactive antibodies were investigated further using agglutination tests with liposomes made from pure auxiliary lipids (cholesterol and lecithin) or containing in addition either galactocerebroside, sulfatide or a mixture of bovine brain gangliosides. The great majority of myelin liposome agglutinating antibodies reacted with all types of liposomes, including those made from pure auxiliary lipids. Investigations by ELISA suggest that phospholipids are the reactive components, at least for some of these mAbs. Some antibodies reacted with liposomes containing galactocerebroside or sulfatide, others only with sulfatide containing liposomes. Antibodies showing these specificities were only obtained from MS patients.

Multiple sclerosis in the Faroe Islands. IV. The lack of a relationship between canine distemper and the epidemics of MS

Clinical onset of multiple sclerosis (MS) occurred in 32 native resident Faroese between 1943 and 1973, comprising 3 consecutive epidemics of decreasing frequency. Relationship of MS with the appearance of canine distemper (CD) was explored by serologic studies, questionnaires, and veterinarian reports. Tested were sera from 12 MS patients and 112 controls among the 22 patients and 192 controls with questionnaires in 1978-1979. The daily treatment ledgers of the Veterinarian of the Faroes 1940-1961 were also reviewed and additional Faroese interviewed 1987-1988 as to CD. History of CD was determined for residence of all 32 MS. There was no evidence of elevated CD antibody titers in MS vs controls for neutralizing titers or ELISA values, nor to ELISA for measles. In the questionnaires only one patient and 2 of his sibs reported owning (the same) dog(s) with CD during the war. One other patient reported a possibly sick dog but not CD. CD occurred in one southern village 1941-1942, was present on Vágar from 1941-1950, and was epidemic on Streymoy 1944-1945 with scattered cases there and elsewhere through 1950. There was no significant correlation between villages with CD and MS residents. We conclude that the occurrence of multiple sclerosis was not related to the presence of canine distemper or sick dogs in the Faroe Islands.

Autoimmunity in demyelinating diseases

Demyelinative diseases of the CNS and peripheral nervous system can be distinguished on the basis of primary mediation by antibody or T lymphocytes (or failure of the T-cell-mediated response) and on the basis of chronicity. The principal mechanisms are autoimmunization to myelin antigens after actual immunization with tissue or infection with cross-reactive viruses or, alternatively, persistent infection of the nervous system (viral or spirochetal) with an associated immune response to the pathogen.

Epidemiological investigations into multiple sclerosis in southern Hesse. II. The distribution of cases in relation to exogenous features

In order to discover possible exogenous variables associated with a higher multiple sclerosis risk, the distribution of cases with definite and probable multiple sclerosis ascertained in the course of a micro-epidemiologic study in Southern Hesse was evaluated and compared with some environmental factors. The prevalence in 1980, the prevalence of cases with disease-onset within the region according to locality of onset and the rate of native Southern Hesse patients according to childhood residence all showed a similar geographical distribution, with the highest values in the south-eastern, mountainous part of the region. This district has a lower annual mean temperature, more annual snow-days and a higher annual precipitation compared to the remaining area. A statistical comparison revealed no association with industrial or agricultural activities, with a particular type of land use, with cattle, pig- or horse-breeding, or with sanitary or housing standards. On the other hand, a slight association with the soil type could be demonstrated, with higher rates on loam and clay subsoils when compared to predominantly sandy regions. Whether this finding has any significance or not remains to be clarified.

Genetic analysis of multiple sclerosis in Shetland

In a family study of all patients with multiple sclerosis in Shetland the number of inbred patients, although high for Britain and higher than in Orkney, is not higher than the number among controls, and the inbreeding coefficients suggest that there is no recessive involvement of rare genes in the aetiology. The kinship coefficients show close interweaving of ancestries of patients and controls and eliminate from the aetiology any involvement of recently introduced single genes dominant or codominant in effect. Family histories show that single locus inheritance is unlikely. Any genetic involvement is likely to be polygenic, but on a multifactorial hypothesis the estimates of heritability are very low. The findings suggest that the genetic contribution to the aetiology of the disease in Shetland is slight.

A study of measles virus and canine distemper virus antibodies, and of childhood infections in multiple sclerosis patients and controls

We investigated the levels of neutralizing antibodies to measles virus and canine distemper virus (CDV) in 72 multiple sclerosis patients (MS) and matched controls and also examined the frequency and age of onset of a number of childhood illnesses, including measles. The frequency of each childhood illness was not significantly different between cases and controls, but cases did report a later age at measles infection. Our data suggest that the risk of MS is increased by a factor of 1.9 if measles infection occurs between 5 and 9 years of age. A validity survey, based on a questionnaire to general practitioners, suggested substantial inaccuracy in the patients' reports of when they had measles, but the direction and degree of inaccuracy did not appear to be different between cases and controls. We also found higher titres of neutralizing antibodies in cases than controls to both measles virus and CDV, although the CDV difference was not statistically significant. In the light of a significant correlation between measles and CDV titres in both cases and controls, we used paired logistic regression to determine if the case-control difference in titres for each virus could be explained by a confounding effect on one by the other. The numbers were too small, however, to enable us to separate out any independent association of either virus with MS.

Multiple sclerosis and dog ownership. A case-control investigation

In 1977 and 1978 Cook and his associates demonstrated a positive association between ownership of small dogs and both familial and sporadic cases of multiple sclerosis in New Jersey. Because of the far reaching implications of this work, a similar study was carried out and 72 patients with clinically definite multiple sclerosis (MS) who were resident in the area covered by the Oxford Regional Health Authority, were interviewed to ascertain their past exposure to housepets and other animals. Two hospital controls were chosen for each patient matched for age and sex and area of residence, and these were interviewed in the same manner as the MS cases by the same interviewer, usually in the patients' homes. Similar proportions of cases and controls had resided in a household with a dog at some time prior to the onset of their disease and there was no evidence that cases had lived with more dogs or had lived with them for longer periods than had controls. There was no indication that cases had greater exposure than controls to dogs or any other housepet in the early years of their life or in the period immediately prior to disease onset. Our data suggest that exposure to housepets and other domestic animals is unlikely to be an aetiological factor in MS.

How multiple sclerosis is related to animal illness, stress and diabetes

At the University of Alberta's multiple sclerosis research clinic 100 patients with multiple sclerosis were matched to control patients for age, sex, race and zone of residence before the age of 15 years. Case and control subjects were interviewed and information was collected by questionnaire on factors that might play a role in the development of multiple sclerosis. The only factors found to be significantly associated with the development of this disorder were a history of leisure time spent in physical activities before the onset of symptoms, exposure to animal illness -- specifically canine distemper -- and a history of severe or prolonged emotional stress. The study also confirmed a familial predisposition to multiple sclerosis and suggested a relation between the disorder and a personal or family history of diabetes mellitus.

Multiple sclerosis in the Orkney and Shetland Islands. IV: Viral antibody titres and viral infections

A controlled serologic survey of antibody titres to 17 viruses was undertaken in multiple sclerosis patients in the Orkney and Shetland Islands. No consistent pattern of elevated antibody titre levels or the presence of antibody was noted in patients compared with two control groups. Because of the isolation of these islands, the mean age at acquisition of common childhood infections, including measles, was considerably older than that of inhabitants of Europe and the United States of America. The age of occurrence of varicella was consistently younger in patients than in controls. Of note is the fact that six patients had measles after the onset of MS. This study failed to incriminate any of the viruses tested in the aetiology of MS.