Tissue culture protocols for the obligate parasitic plant Striga hermonthica and implications for host-parasite co-cultivation

Striga is a genus of parasitic plants that poses great danger to livelihoods of millions of smallholder farmers in sub-Saharan Africa by limiting production of staple cereals. The parasite attaches to the roots of the crop and establishes a vascular connection with the host’s xylem vessels in order to access water, organic and inorganic nutrients, leading to stunted growth and death of the infected plant. Mechanisms underpinning host–parasite interactions are not clearly understood making well-informed strategies for control of the parasite difficult. To facilitate studies of Striga–host interactions for molecular and genetic studies, we: (i) established an efficient protocol for growing Striga from seeds in tissue culture; (ii) optimized protocols for its regeneration through direct organogenesis and somatic embryogenesis, and (iii) determined the effect of co-culturing host and parasite in the same culture media. We found the best auxin and cytokinin concentrations to be: 10.7 μM naphthaleneacetic acid (NAA) and 2.2 μM 6-benzylaminopurine (BAP) for embryogenic callus regeneration and 1.1–4.4 μM BAP without NAA for shoot multiplication. While seedling, stem and leaf explants induced callus with the same frequency, seed radicles did not produce any callus. Unexpectedly, we found that when Striga callus was added in rice growing on culture media, the parasite adversely affected the host through formation of lesions on leaves and resulted in less shoot induction from callus in the parasite. Techniques described in this study will enhance further understanding of Striga–host interactions

Ehrlichia spp. close to Ehrlichia ruminantium, Ehrlichia canis, and “Candidatus Ehrlichia regneryi” linked to heartwater-like disease in Kenyan camels (Camelus dromedarius)

We present findings from an outbreak of a heartwater-like disease in camels that killed at least 2000 adult animals in Kenya in 2016. Clinical signs included excitability, head pressing, aimless wandering, recumbency, and fast breathing followed by death after about 4 days. The observed morbidity in one herd was 40% with an average mortality of 7.5% in animals that received early antibiotic treatments. In untreated adults, the case fatality rate reached 100%. Gross pathology showed pulmonary edema, pleural exudate, hydrothorax, hydropericardium, ascites, enlarged “cooked” liver, nephrosis, and blood in the abomasum and intestine. Using established PCR-based protocols for tick-borne pathogens, a sequence close to Ehrlichia regneryi and Ehrlichia canis amplified in blood from two sick camels. We also amplified an Ehrlichia sp. sequence close to Ehrlichia ruminantium Welgevonden from a pool of Amblyomma spp. ticks collected from a sick camel and in a pool of Rhipicephalus spp. ticks from healthy camels