Abstract
Herd types of B-str. were determined for 159 herds on the basis of serological typing of 336 quarter-milk isolates. The herds were selected at random within an area with some 25,000 herds, and assumably the results reflect the type distribution in that area. In contrast with previous findings in Zealand, no significant difference in the distribution of herd types was found between new-infected herds and herds with infections of known duration. However, compared to herds with infections of presumably long standing, newinfected herds had a relative deficit of Herd Type III.
Herd Types III and X showed a significantly higher tendency than the other types to spread among cows within a herd.
It is concluded that infections caused by Herd Types III, Ia/III and X require special attention in a control program, while in most cases supervision would seem to be adequate for infections caused by other types. Yet, such a program will leave a hygienic problem unsolved.
Keywords: Group-B streptococci, serological types, herd-type distribution
Sammendrag
Ved hjælp af serologisk typebestemmelse af 336 kirtelprøveisolater hidrørende fra 159 besætninger fordelt i 3 jyske og det fynske mastitisbeksempelsesområde kunne gruppe B-streptokok (B-str.) besætningstypefordelingen fastlægges med en acceptabel sikkerhed for et samlet kontrolomrde p ca. 25.000 bessetninger (626 B-str. inficerede i Oktober kvartal 1979, 4ø8 B-str. nyinficerede i 1979).
I modsætning til hvad der var fundet for det sjællandske bekæmpelsesområde viste resultaterne ingen vaesentlige forskelle i besætningstypefordelingen mellem nyinficerede bessetninger og bessetninger, hvor B-str. infektionen havde bestet en (kendt) periode. Besætningstype III var dog relativt underrepræsenteret, nr nyinficerede bessetninger sammenlignedes med bessetninger med meget langvarige infektioner (Tabel 1).
Blandt køer inden for den enkelte smittede besætning udviste besætningstyperne III og X en signifikant højere spredningstendens end de øvrige typer (Tabel 2).
Det konkluderes under hensyntagen til resultaterne fra det sjællandske materiale, at infektioner forårsaget af bessetningstyperne III, Ia/III og X kræver særlig opmærksomhed i et kontrolprogram, medens overvågning i de fleste tilfælde synes at vsere tilstrækkeligt for infektioner forrsaget af de øvrige typer.
Et bekæmpelsesprogram efter sdanne retningslinier vil imidlertid lade et hygiejnisk problem – B.str. forekomst i den rå mælk – være uløst.
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