Serum antibody responses and haemolytic complement activity were evaluated in White Leghorn (WLH) and Rhode Island Red (RIR) chickens that were vaccinated with live-attenuated vaccines of Newcastle disease virus, or infectious bronchitis virus, or infectious bursal disease virus by means of ocular challenge at 10 times the normal vaccination dose. Complement titres in non-vaccinated birds were significantly higher in WLH birds compared to RIR birds. The lentogenic viral infection resulted in an immediate stimulation of complement activity, followed by a decrease to initial complement levels within 2 weeks post vaccination, when the antibody response took over immune defence. As compared to WLH chickens, RIR birds mounted a faster and significantly higher antibody response to the vaccine viruses used. In WLH hens, significantly higher haemolytic complement activity post vaccination was found as compared to RIR hens. Possible consequences of the observed differences in immune responsiveness of the two breeds to viral vaccines are discussed.

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.

To study the relation between serum complement levels and the chicken MHC (B) complex, complement haemolytic activity was measured in sera from hens from seven pure-bred B-typed White and one Brown Leghorn lines, and three ISA-Warren lines that had been divergently selected for antibody responses to sheep red blood cells (SRBC). Significant differences occurred in the serum haemolytic complement activities, both belonging to the classic (CPW) and the alternative (APW) pathways, among the 11 different haplotyped chicken lines. Hens with high CPW and high APW titres predominantly displayed the B2 or B21 haplotypes. Chickens with low CPW and APW were found in B14 and B15 haplotypes. Haplotype B14 appears to be different in complement levels when present into the pure-bred lines or into the ISA-Warren line selected for low antibody responses to SRBC. Otherwise, the presence of B21 in ISA-Warren line selected for high antibody responses to SRBC does not differ with the B21 in the inbred lines (except in the NL-line for CPW values). In general the haplotypes B2 and B21 are found in chicken lines with enhanced disease resistance, and the B15 haplotype has been connected with enhanced disease susceptibility. Our results suggest that levels of haemolytic complement activity, either from the classical or from the alternative pathways, may underlie part of the immunocompetence ascribed to the MHC (B) complex in chickens.

German Dahlem Red chickens with three different major genes of tropical interest: Nana– (naked neck), Ff– (frizzled) and dw– (dwarf), respectively, were tested for serum haemolytic complement, which is essential in innate host defence against infectious agents. Eight different combinations of genes for body size and feather coverage were evaluated. Significant differences both for both the calcium-dependent (classical, CPW) and the calcium-independent (alternative, APW) complement titres were found between the phenotypes. Phenotype nanaffDw– showed the highest complement status. The frizzled (Ff–) gene had a negative influence on APW titres, whereas the dwarf (dw–) gene had a negative influence on CPW titres. The naked neck (Nana–) gene had various influences on the haemolytic complement status. All tested hens had MHC (B) 21 haplotypes, whereas the gene for dwarfism appeared to be linked with the B19 haplotype. It was concluded that introducing major genes (Nana–, dw–, Ff–) to conquer environmental stress in hot climates can have a negative impact on certain aspects of the innate immunity of poultry.

As part of a series of studies to characterize innate and specific immune responses of indigenous chicken lines, birds from Bolivia and India were screened serologically for MHC class IV (BG) polymorphism by direct haemagglutination using haplotype-specific antisera (B2, B4, B12, B13, B14, B15, B19, B21). The sample consisted of 95 Bolivian indigenous chickens and 119 hens from the four most common North Indian ‘back-yard’ chicken lines: Yellow Aseel (AP), Kadaknath (KN), frizzled typed (Ff–) and naked neck (NN). Of all chickens tested, the majority were haplotyped as B2, B15, B19 and B21. Of the Bolivian chickens, 89.5% could be haplotyped: 54.9% were homozygous (including 43.3% B15), and 34.6% were heterozygous (including 15.7% B15). B2-like haplotypes were not found among the Bolivian hens, and only 3.2% of these birds showed homozygous B21-like proteins. Of the Indian hens, MHC (BG)-like proteins could be detected in 60.0% of the AP birds, 6.7% of the KN birds; 40.0% of the Ff– birds; and 10.3% of the NN birds. In these lines, a total of 40.1% (AP), 6.7% (KN), 30.1% (Ff–) and 10.3% (NN) were homozygous for the B-haplotype. Only in the AP line (19.9%), and the Ff– line (9.9%) were heterozygous B-haplotypes types found. The B2 haplotype was found in all Indian chicken lines. Most Indian birds have completely unknown haplotypes, indicating a potentially interesting genetic pool. Subgrouping the Bolivian and Indian indigenous hens into monomorphic BG populations revealed individual differences based on the B-types.

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 in indigenous hens are not solely dependent on local antigenic pressure but may also depend on genetic 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.

Antibody responses, serum complement haemolytic activity, and complement component C3 and Factor B consumption were studied in chickens divergently selected for high and low antibody responses to sheep red blood cells, and in a randombred control line. Significantly higher total and IgG antibody responses to SRBC were found after intramuscular immunisation in the high antibody responder (H) line versus the low antibody responder (L) line and the control (C) line. Also significantly higher antibody titres were found in the C line as compared to the L line. Ca-dependent (classical) and Ca-independent (alternative) complement haemolytic activity was significantly higher in the H line than in the L line. Also initial complement haemolytic activity and C3 levels prior to immunisation with SRBC were significantly higher in the H than in the L line. The L line, on the other hand, showed numerically higher Factor B levels. Immunisation with SRBC was followed by a different consumption of C3 in serum of the H line than the L line. The results indicated that divergent selection of chickens for specific antibody responses to SRBC affected complement levels and C3 consumption in these chickens. This suggests a genetic linkage between these two immune traits.

Seroprevalences to three infectious agents were studied in rural poultry farms in three different ecological regions in Benin. Of 260 sera, 65% were seropositive for Newcastle disease virus, 10% for Salmonella pullorum and 62% for Mycoplasma gallisepticum.

Sera from cattle and sheep stored at -70, -20 and -10-degrees-C were examined for haemolytic complement at Days 0, 37, 54, 86, 133 and 245. The decline in complement followed a similar trend, both by classical pathway (CPW) and alternative pathway (APW) assay methods. Both cattle and sheep sera retained 80% of their complement activity till Day 245 at -70-degrees-C whereas at -20-degrees-C cattle sera had lost 67% and sheep sera 80% of the activity. At -10-degrees-C the decline in complement levels was, in general, similar to -20-degrees-C. The complement level of sheep sera declined more rapidly than that of cattle. For reliable results, it is suggested that sera of cattle and sheep should be assayed for complement within 4-5 months at -70-degrees-C and within a month at -20 or -10-degrees-C.

Although 65% of domesticated birds in the Cameroon are kept in traditional chicken farms, very little attention is given to this important sector by the administration as well as by the farmers themselves. This could be detrimental to the modern poultry sector where a lot of investments have been made during recent years. In order to estimate the danger of neglecting traditionally-raised chickens and the health threat they represent for the poultry population of the country, a study was conducted to evaluate the impact of Newcastle disease in traditional farms. A total of 180 chicken blood serum samples from three provinces of the Cameroon were submitted to the haemagglutination inhibition test; 51.66%, 48.33% and 46.66% of birds respectively from the East, West and North provinces reacted positively to the test. The consequences of such a situation are emphasised.

Blood of different breeds of cattle, namely Lagune from the Atlantic province, Borgou and Borgou x Zebu from the Borgou province, and Somba and Zebu from the Atacora province of Benin, were examined for trypanosome infection. Thick and thin blood smears for trypanosomes, the card agglutination test (CATT), indirect immunofluorescent antibody test (IFAT) and trypanolytic test for antibodies to trypanosomes were used. Trypanosomes were detected in 19.3% (range 9.8-31.4%) of animals by examination of blood smears; antibodies to trypanosomes were found in 89.8% (range 88.4-100%) of samples by IFAT, 50.6% (range 34-87.5%) by CATT and 3.4% (range 1.1-7.1%) by trypanolytic test. Trypanosoma vivax and Trypanosoma congolense were the main species in Benin with a low number of Trypanosoma brucei. Zebu had lower infection rates than trypanotolerant breeds of Benin. The infection rates of various trypanotolerant breeds were not significantly different.