Sizes and developmental viability of sequentially oviposited eggs of dog ticks: Rhipicephalus sanguineus and Haemaphysalis leachi leachi.

Sizes and developmental viability of sequentially oviposited eggs of up to 12th day oviposition by dog ticks Rhipicephalus sanguineus and Haemaphysalis leachi leachi were studied. The mean length and breadth of eggs oviposited on days 1 and 2 were greater (0.45 +/- 0.111 and 0.44 +/- 0.042) than those of subsequent ovipositions. The eclosion periods of eggs laid from 7th to 12th day of oviposition were progressively shorter (17, 16, 14 and 19, 17, 0 days) than those of eggs laid on days 1 and 2 (20 and 22 days) by R. sanguineus and H. leachi leachi, respectively. The percentage mortality of eggs of days 11 and 12 oviposition (70.3% and 100%) was significantly higher than that of earlier ovipositions (9.6% and 31.7%) for R. sanguineus and H. leachi leachi, respectively. The numbers of larvae which engorged on rabbits after hatching from eggs of 11th and 12th day oviposition (43 and 0) were significantly fewer than those which hatched from eggs of days 1 and 2 (79 and 63) for R. sanguineus and H. leachi leachi, respectively. A total of 383 larvae of R. sanguineus engorged on rabbits compared to 225 larvae of H. leachi leachi. It is concluded that eggs of early ovipositions of R. sanguineus and H. leachi leachi are longer and wider and more viable than those laid later in the oviposition cycle. The significance of these findings in terms of hatchability of eggs is discussed.

Comparison of two clinic-based immunoassays with the immunofluorescence antibody test for the field diagnosis of canine monocytic ehrlichiosis.

The aim of this study was to compare a clinic-based enzyme-linked immunosorbent assay (immunocomb-Eliza, Biogal, Israel) and a field-based dot-blot enzyme-linked immunoassay (DBELIA) with the indirect immunofluoresence antibody test (IFAT) used for the field diagnostics of canine monocytic ehrlichiosis (CME). The total test samples was 60; out of them 52 serum samples came from naturally exposed police German shepherd dogs and 8 from adult mongrels infected with viable Ehrlichia canis propagated in a dog macrophage laboratory cell line (DH82). The DBELIA test was positive in 86.7% (56/60) and negative in 13.3% (8/60), while the immunocomb-Eliza was positive in 91.7% (55/60) and negative in 8.3% (5/60). IFAT revealed 90.0% (54/60) of DBELIA samples as positive while 10.0% (6/50) as negative, with an agreement of 83.3% (50/60). IFAT revealed 96.7% (58/60) of immunocomb-Eliza samples as positive and 3.3% (2/60) as negative, with an agreement of 91.7% (55/60). There was an overall agreement of 86.7% (52/60) among the three assays. Five (62.5%) of the 8 disagreement were of low IFAT, titre range < 1:240 attributable to false initial IFAT results from non-specific antibody binding, cross-reactivity or antigenic variations. A positive correlation was observed in the results of the 3 assays with correlation coefficients (r2) of 0.8214 at P < 0.0001 and 0.8984 at P < 0.001 for IFAT-DBELIA and IFAT-immunocomb-Eliza, respectively. No statistically significant differences were observed in their results. The chi-square values were 0.9021, P-0.3142 and 0.04322, P-0.7624 for DBELIA and immunocomb-Eliza, respectively. Sensitivities and specificities were 92.6%, 83% and 96.0%, 87.0% for DBELIA and immunocomb-Eliza, respectively. When based on IFAT titre range of over 1:240. Both assays were sensitive and specific for the field diagnosis of CME but the immunocomb-Eliza is more sensitive and specific than the DBELIA, but the latter saves time, requires no special equipment and personnel and has a preservable shelf-life (>1 year) for its dot-antigen package.

Non-immune control of trypanosomosis: in vitro oxidative burst of PMA- and trypanosome-stimulated neutrophils of Boran and N'Dama cattle.

An in vitro assay that measures the generation of superoxide anions (O2-) was used to assess the level of oxidative burst of phorbol myristate acetate (PMA)- and trypanosome-stimulated neutrophils isolated from healthy Boran and N'Dama cattle, and those infected with Trypanosoma congolense. PMA stimulation of healthy bovine neutrophils resulted in between 300-400 % increase in O2- generation. Neutrophils of Boran cattle exhibited slightly higher but insignificant O2- generation capacity than those of the N'Dama breed. In vitro stimulation by trypanosomes of neutrophils isolated from Trypanosoma congolense-infected cattle caused significant increases in O2- generation, especially on days 14, 28 and 42 post-infection, of both breeds of cattle. No significant differences were observed in O2- generation capacity of the neutrophils of both breeds of infected cattle throughout the period of assay. The results of this study have shown that PMA and trypanosomes do cause an enhanced in vitro oxidative burst, hence trypanosome phagocytosis and killing activity of neutrophils. Neutrophils have been shown to play very significant roles in parasite clearance, hence reduction of trypanosome parasitaemia. The rates of both in vitro generation of O2- and trypanosome phagocytosis over time did not differ significantly between Boran and N'Dama breeds of cattle, even during T congolense infection in this study. Hence, it may be inferred that sustained and higher parasitaemia, more pronounced neutropenia, inadequate bone marrow response and less effective trypanosome-specific immune response, rather than defective neutrophil trypanosome destruction, may be the problem of trypanosusceptible cattle breeds.