Lithium Chloride Shows Effectiveness against the Poultry Red Mite (Dermanyssus gallinae)

Abstract

The poultry red mite (Dermanyssus gallinae) is the main pest of poultry, causing severe problems by being a vector of several animal and human pathogens. The number of miticides is few, and their efficacy in practice implies problems of residues and resistance; therefore, the demand for a new and safe agent is constant. The present publication investigated the effectiveness of lithium chloride under in vitro conditions on poultry red mites. This chemical currently appears to be one of the most promising alternatives to study amongst potential applicants to treat varroosis, a fatal disease of honey bees. In Experiment I, the previously used experimental doses (5.52 M, 2.76 M, 1.38 M) on Varroa mites confirmed their in vitro activity on the poultry red mite. Three event times (uncontrolled movement, immobilisation and death) were recorded to base the response to treatment for each concentration. In Experiment II, the LD 50 value was calculated, i.e., the value at which 50% of the mites were killed by the treatment. This Experiment showed that the LD50 of lithium chloride = 0.265 M in the poultry red mite. It is to note that the study remained restricted to in vitro confirmation of lithium chloride's effectiveness on the parasite. Thus, further extensive studies are needed to decide whether it has any relevance in practice against D. gallinae, and also to assess potential residue problems that could affect poultry products.

Keywords: contact effect; lithium chloride; poultry red mite.

Figure 1

Mean exposure time from immersion to occurrence of an event, with error bars denoting ± SE (standard error) of the mean, by LiCl concentration. For statistics based on LOG₁₀(x + 1) transformed data, see Table 2.

Figure 2

Abbott corrected mortality rates and fitted trends for the three LiCl-concentrations.

Figure 3

Concentration-response curve and LD50 concentration value for lithium chloride in poultry red mite. Note that LD50 value was calculated based on the net effect of the tested substance (i.e., mortality above the control level).