Age-related infection and transmission patterns of human cysticercosis.

Neurocysticercosis is recognised as an important but neglected cause of epilepsy in developing countries where the parasite occurs. Data on the transmission dynamics of the parasite in endemic areas are scarce. Individuals living in these areas are likely to be highly exposed to the parasite, but relatively few of them develop active infections. The present study aimed to describe and gain insights into changes in antibody responses and infection patterns related to age and/or gender in a south Ecuadorian rural population by combining antibody and antigen serological data with demographic characteristics. In 25% of the population, antibodies to Taenia solium cysticerci were detected whilst 2.9% had circulating parasite antigens. The proportion of antibody-positive individuals increased significantly until the age of 40years to become stable in older individuals. A rule-based simulation model was developed to explain these variations and to reflect the dynamics of exposure to, and transmission of, the parasite. In contrast, the proportion of people presenting circulating parasite antigens, reflecting an active infection, was significantly higher in people older than 60years. Immunosenescence could explain such an observation since a weaker immune system in the elderly would facilitate the establishment and maintenance of viable cysticerci compared with fully immunocompetent younger individuals. This work points out the role of the immune system in the development of cysticercosis within an exposed population and highlights new essential issues in understanding the transmission dynamics of the parasite, its incidence and the resulting immunological response at a population level.

Haemolytic complement activity and humoral immune responses to sheep red blood cells in indigenous chickens and in eight German Dahlem Red chicken lines with different combinations of major genes (dwarf, naked neck and frizzled) of tropical interest.

A total of 376 chickens from different ecotypes were immunized with the non-pathogenic multi-determinant antigen sheep red blood cells (SRBC). The ecotypes included indigenous chickens from various locations in Tanzania (n=102), India (n=86) and Bolivia (n=89). In addition, eight German Dahlem Red (GDR) chicken lines with different major genes (dwarf, naked neck and frizzled) of tropical interest were also immunized with SRBC. Immune competence of the breeds was assessed by measuring complement haemolytic activity, both from the classical calcium-dependent complement pathway (CPW) and alternative calcium-independent complement pathway (APW), alongside IgTotal, IgG and IgM antibody responses to SRBC at 7 days post immunization. Large variations in complement activity and antibody responses to SRBC were observed within and between the indigenous breeds. Many indigenous chickens, especially from Bolivia, showed decreased complement activity (APW) following immunization with SRBC. Breeds from India showed the highest CPW activity and humoral (especially IgM) responses to SRBC, suggesting high immune competence. In contrast, Bolivian chickens were characterized by low CPW activity, low APW activity and low antibody levels to SRBC suggesting an overall low immune competence. In the GDR chickens, characterized by high CPW activity and high IgG antibody responses to SRBC, the major genes for naked neck, frizzling and dwarfism had no significant effect on the antibody responses and complement activity to SRBC.

Different serum haemolytic complement levels in indigenous chickens from Benin, Bolivia, Cameroon, India and Tanzania.

Titres of classical (CPW) and alternative (APW) complement pathways were measured in clinically healthy local chicken populations (ecotypes) from Africa (Benin, n = 78; Cameroon, n = 299; Tanzania, n = 101), Asia (India, n = 96) and South America (Bolivia, n = 64). A wide variation was found in haemolytic complement levels between the various ecotypes. Distributions of the classical and alternative complement titres were not normal but were skewed to the right. Differences in complement were found both within and between ecotypes. Furthermore, CPW titres of the indigenous chickens were lower than those determined in commercial layer chickens. This suggests that complement levels background and husbandry. The relationships between complement levels, the chicken MHC(B) complex, environmental antigenic pressure, and survival of the scavenging local chickens are discussed.