The Occurrence of Summer Mastitis in Jutland (Denmark) in Relation to Meteorological Factors

Abstract

Data for incidence of summer mastitis in 14 veterinary practices in Jutland (Denmark) were related to meteorological factors using statistical methods. A correlation and regression analysis showed that summer mastitis occurred earlier in years with high temperature and precipitation in early summer. The annual number of cases markedly increased over the years 1953 to 1980. This increase was described by applying a linear increase with with year to a logarithmic transformation of the annual incidence.

Analysis of 10-day incidences from the veterinary practices and daily incidence from a test site at St. Vildmose (Jutland) showed that incidence of summer mastitis could be related to temperature and wind velocity within the previous 10 days. High temperature and low wind velocity in this period increase the incidence. This indicates that the incubation period of summer mastitis is at maximum about 10 days. The activity of the fly (Hydrotaea irritans Fall), which acts as mechanical vector for the bacteria is influenced by temperature and wind velocity. This may explain the variation in incidence of summer mastitis during the season and from year to year.

Sammendrag

Data for incidensen af sommermastitis i 14 veterinære praksis-områder i Jylland (Danmark) sammenholdtes med meteorologiske faktorer ved anvendelse af statistiske metoder. En korrelations- og regressionsanalyse viste, at sommermastitis forekommer tidligere i år med høj temperatur og nedbør i forsommeren. Den årlige incidens stiger stærkt op gennem årene fra 1953 til 1980. Denne stigning kunne beskrives som en lineær stigning i en logaritmisk form af den årlige incidens.

Analyse of 10-døgns incidensen fra de veterinære praksis-områder og af den daglige incidens fra et forsøgsområde i St. Vildmose (Jylland) viste, at incidensen af sommermastitis afhænger af temperatur og vindhastighed i de foregående 10 dage. Høj temperatur og lav vindhastighed i denne periode forårsager en stigning i incidensen. Dette indikerer, at inkubationstiden for sommermastitis maksimalt er ca. 10 døgn. Temperatur og vindhastighed påvirker formentlig aktiviteten af de insekter, der virker som vektorer for sygdommen, med deraf følgende påvirkning af den kliniske sygdoms incidens.