Abstract
Christensen, S. AA. Henriksen: Shedding of oocysts in piglets experimentally infected with Isospora suis. Acta vet scand., 1994, 35, 165-172.–Forty-seven piglets were inoculated with doses of 100 to 50,000 sporulated oocysts of Isospora suis. After 5-7 days oocysts were found in faeces. The patent period extended from 8 to 16 days. The shedding of oocysts showed a cyclic pattern with 2-3 peaks separated by intervals of approximately 5 days. Subpatent periods were often seen between the peaks.
The level of oocyst shedding during the initial days of the patent period reflected, to some extent, the inoculation dose. However, a maximum of OPG at the 100,000 level was observed among one or more piglets from all groups, regardless of the inoculation dose. Among the majority of piglets inoculated with more than 100 oocysts, the highest OPG-figures were observed in the first peak of the cyclic pattern. Unlike this, the maximum of OPG was observed in the second peak of the cycle among 6 of the 7 piglets inoculated with 100 oocysts only. The triphasic pattern was most pronounced in the low dosed group.
The marked upscaling of oocyst production, as particularly registered in the low dosed groups, seams to explain at least part of the problems met under practical conditions, when trying to eliminate the transmission of oocysts between successive litters in the farrowing boxes.
The cyclic excretion pattern and an apparent absence of autoinfections may indicate that the development of I. suis in the host includes several oocyst producing generations descending from the same initial infection.
The presence of subpatent periods can probably explain the marked variation in OPG, as they are often recorded when examining faecal samples from piglets, even when the samples are originating from the same litter.
Keywords: coccidiosis
Sammendrag
47 pattegrise blev hver podet med en dosis af sporulerede oocyster af Isospora suis. Dosis varierede fra 100 til 50.000 oocyster. Oocystudskillelse begyndte 5-7 dage efter podning Patensperioden udstrakte sig over 8-16 dage Udskillelsen af oocyster fulgte et cyklisk mønster karakteriseret ved 2-3 toppe, som var adskilt af lntervaller på ca. 5 dage. Subpatente perioder blev ofte observeret mellem toppene. OPG-niveauet (OPG = oocyster pr. g fæces) i den første del af patensperioden afspejlede i nogen grad lnfektionsdosis. OPG-værdier over 100.000 blev dog konstateret blandt et eller flere dyr i alle grupper, uanset lnfektionsdosis. Hos de fleste af de grise, som var podet med mere end 100 oocyster, konstateredes de højeste OPG-værdier i forbindelse med 1. top ι det cykliske forløb. I modsætning hertil kulminerede oocystudskillelsen fra 6 af de 7 grise, som kun var podet med 100 oocyster, i 2. top. Det trifasiske forløb var tydeligst aftegnet i den lavest doserede gruppe. Den markante opformering af parasitter, som blev registreret i de gennemførte undersøgelser, specielt i de lavest doserede grupper, synes at kunne forklare ι det mindste nogle af de vanskeligheder, der under praktiske forhold er forbundet med etablering af hygiejniske foranstaltninger i farebokse, som på ef-fektiv made vil hmdre overførsel af smitte fra kuld til kuld.
Det cykliske forløb og et tilsyneladende fravær af autoinfektion synes at lndikere, at I. suis gennemløber en udvikling i værten med flere på hinanden følgende generationer, der alle hidrører fra samme lnitiale infektion.
Tilstedeværelse af subpatente perioder kan formentlig sættes i relation til den betydelige variation i oocystudskiUelse, som hyppigt registreres ved ruti-nemæssige diagnostiske undersøgelser af fæces-prøver fra pattegrise-selv i tilslutning til samtidig undersøgelse af prøver fra forskellige pattegrise i samme kuld.
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Acknowledgments
This study was supported by the Danish Research Academy, Grant No. 41-1401. The authors highly appreciate the skilful technical assistance from Christa Persson, Bolette Hindø and Werner Jensen.(Accepted February 21, 1994).
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