Definition of leptospirosis
"Leptospirosis" is a general term comprising a series of systemic infectious zoonoses, with an acute course, caused by bacteria belonging to the genus Leptospira . Leptospirosis is known by many synonyms, and among the best known are: autumn fever (akiyami, in the Japanese language), seven-day fever (nanukayami, in Japanese), swine fever or - in the case of icteric leptospirosis - swamp fever, mud fever, dog-cutter fever or jaundice hemorrhage.
It is said that towards the end of the eighteenth century a well-known surgeon first described a complex symptomatology of leptospirosis, mistakenly diagnosing it as a plague. To have a correct diagnosis of leptospirosis it was necessary to wait until 1870, while 1917 was the year of identification of the bacterium responsible for the disease. [taken from //it.wikipedia.org/]
Incidence
Globally, leptospirosis is one of the most prevalent infectious syndromes; however, this zoonosis still remains an unknown quantity, a burden that raises considerable concerns in the clinical field, above all because of the little-defined symptomatology and the obvious diagnostic difficulties. In this regard, leptospirosis is heavily underestimated and remains surrounded by a shadow of mystery.
Despite this premise, leptospirosis is considered a cosmopolitan zoonosis, although in most cases the disease is observed in tropical and sub-tropical areas with a humid climate; leptospirosis occurs only rarely with small outbreaks.
In our country, leptospirosis affects, on average, 100 people a year, especially in Veneto.
Globally, the annual incidence is estimated at around 0.1-1 per 100, 000 healthy people living in temperate climate regions, and around 10-100 cases per 100, 000 healthy subjects in tropical areas.
In Europe, leptospirosis is not widespread at all: in France there was a greater incidence of the disease with over 1 case per 100, 000 people. [taken from Zoonosi and public health: a disciplinary approach for an emerging problem, by E. Matassa]
Being a zoonosis, leptospirosis affects mainly domestic animals, birds and reptiles but, following an occasional contact with these infected animals, the infection can also affect humans.
Medical statistics have found a higher incidence of leptospirosis among males, especially during the warm months and early fall. Currently, the disease is in sharp decline, thanks to the vaccination to which the animals are subjected.
Causes
Leptospirosis is caused by serological varieties of small parasites (spirochetes) belonging to the genus Leptospira (Fam. Leptospiraceae). Leptospires are gram-negative bacteria without flagella, have a filamentous body and a typically spiral shape (hence, the name "spirochete"); these slender micro-organisms are particularly widespread in water and wet environments, and are responsible for many zoonoses, including - precisely - leptospirosis. Leptospires are released into the environment through the urine of infected animals (the bacteria reservoir), such as rodents, wild and domestic animals, etc. Animals eliminate leptospires through urine, thus polluting the soil and water.
Contagion mode
We have seen that leptospires nest in rodents, domestic and wild animals; however, the rat and rodents in general certainly represent the most "dangerous" reservoir for transmitting the beat. More specifically, leptospires nest at the level of the host's renal apparatus, thereby infecting the urine. These spirochetes are subtle bacteria, since they can live in symbiosis with the host for many years, without causing any disease. The man is infected by the contact, intake or inhalation of water infected by the urine of the carrier animals.
The contagion between man and man is almost impossible.
Clearly, the chances of infection are directly proportional to the bacterial load present in the infected water / moist soil.
Leptospires can penetrate through:
- Inhalation (human respiratory channels)
- Contact with contaminated water (microlesions / cuts in the skin of man)
- Intake of infected waters
- Bite of a carrier animal
Subjects at risk
Given the possible methods of contagion, it is clear that the categories most at risk include all those people who, for various reasons (eg working), are forced to remain in frequent contact with water or wet lands. Hunters, veterinarians, sportsmen (especially those who practice water sports), miners, farmers, breeders, fishermen and weeders certainly represent the categories most exposed to the risk of leptospirosis.
