Maltese genetically susceptible to polio

Academic warns of possible re-emergence of virus in new form, links susceptibility to disease in Gozo to consanguineous marriages in the past

Jonas Salk discovered and developed the first successful inactivated polio vaccine
Jonas Salk discovered and developed the first successful inactivated polio vaccine

A study by HV Wyatt, an academic from the University of Leeds who spent five years analysing records of polio epidemics before the records were destroyed by vandals concludes that the Maltese are genetically susceptible to the polio virus which may re-occur in another form after the disease is eradicated and immunisation is stopped.

This conclusion is based on the records of 1,072 Maltese cases of poliomyelitis between 1909 and 1964.

Immunisation for polio is still compulsory for Maltese children, along with that for tetanus and diphtheria. But vaccination is usually stopped after 10 years after a disease is totally eliminated. 

But according to Wyatt when polio cases no longer occur and immunisation ceases, “there will still be a danger that a polio or polio-like virus may emerge”.

Wyatt warns that polio or similar viruses may escape from an unsuspected source or may mutate from other enteroviruses, or may even re-emerge after being dormant in the environment. 

“Plans must be made for the possibility that many with genetic susceptibility and no immunity might be infected. It will be prudent to have stocks of vaccine available for an emergency,” according to the study.

He warns that when polio cases no longer occur and immunisation ceases, there will still be a danger that a polio or polio-like virus may emerge. After that time, two per cent of children will be at risk should a virus reappear. But ten years later, there will be cohorts of young people of whom up to 24% will be at risk of paralysis.

Wyatt analysed the 1,072 Maltese cases of poliomyelitis from 1909 to 1964 between 1982 and 1987. 

He took note of the name and date of birth of each child and from this information he subsequently traced the parents, grandparents and great grandparents of those affected by the disease. 

According to the British academic, unknown intruders have since trashed the records.

The study found 70 pairs of siblings affected by the disease. Of these, 13 pairs suffered poliomyelitis in different epidemics even though the younger sibling was born after the elder was paralysed. 27 pairs of siblings affected by the disease were directly related to more than twice as many other polio victims through grandparents and great grandparents. The study also found that families of polio siblings contained more consanguineous marriages.

In an earlier study focusing on cases in Gozo, which was published last year, Wyatt had found evidence of consanguineous marriages among the parents of children affected by polio and even more among their grandparents.

“Within Gozo, the attack rate was greater in some villages and this was caused by some extended, related families with genetic susceptibility to polio,” Wyatt concluded.

In Nadur Wyatt had found that out of 29 cases of polio, 23 cases were found in a “tightly knit group of families linked by consanguinity.”

Both studies were published in the Malta Medical Journal.

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