Antibody studies in coots (Fulica atra) to Russian spring-summer encephalitis (CEE) virus in the Netherlands. The behaviour of this virus in experimentally inoculated coots

A survey was done with the serum specimens of 156 wintering coots (Fulica atra) in the Netherlands for the presence of antibody against the R. S. S. E.-CEE group of viruses. Although in ten sera neutralization indices were found which undoubtedly should indicate the presence of neutralizing antibody against these viruses, the more or less defective technique of harvesting the blood from the birds which had been shot does not allow the authors to give a final conclusion. Experiments with fluid collected from the crop and gizzard have shown that only a slight contamination of the blood with this fluid at the moment the head is cut off, may give rise to the finding of neutralization indices up to 10,000 in the contaminated serum. Subsequent to this serological survey, viraemia was demonstrated in coots following experimental infection. After subcutaneous inoculation of CEE virus (Graz I strain) it was found in the blood of these coots for 7 to 9 days in demonstrable quantities and to peak titers of 3.0-4.0 log LD50/0.03 ml. of blood generally on the 4th to 6th day post-exposure. In one coot one month after experimental inoculation virus was isolated from the brain, but not from the blood and other tissues tested. No histological examination was performed of the brain of this coot. The significance of this observation is discussed with relation to the role birds can play in nature as potential long-term reservoirs and disseminators of this virus over long distances when migrating or as sources of arthropod infections. Pools of mites from the experimentally infected coots collected on the 3rd and 10th day post-infection, were negative for virus. This study does not all attempt to designate coots as playing a role in the circulation or survival of R. S. S. E. virus in nature. © 1961 Springer-Verlag.