SOME PAST AND ONGOING PROJECTS: FIELD INVESTIGATIONS

Molecular detection of Rickettsia africae in ticks from Cameroon

Andrea  Vanegas,Christian  Keller,  Andreas Krueger,  Ralf Matthias  Hagen,  Hagen‚ Frickmann,

Alexandra Veit, Bernhard Fleischer, Manchang Tanyi, Mbunkah Daniel Achukwi*, Sven Poppert.

*TOZARD PO Box 59 Bambili-Bamenda Cameroon

Introduction

Tick-borne rickettsioses are emerging zoonotic infections in many African countries.  R.  africae  is  the  most  frequent  rickettsia  species  with  human  pathogenic  potential  in  Africa.  It belongs to the group of spotted fever group rickettsiae and transmission is caused by Amblyomma ticks. Human pathogens of the order Rickettsiales have been detected in blood samples of patients with  acute  febrile  illness  and  ticks  samples  in  the  South  of  Cameroon.  Serological  studies  carried out  in  humans  from  different  areas  in Cameroon  have  demonstrated  previous  infections  with Rickettsia spp.. However, the geographical distribution and the prevalence of R. africae in their tick vectors from the North region of Cameroon are unknown.

Materials and Methods

Tick samples were collected from cattle in the central slaughterhouse in Ngaoundere Adamawa region, Cameroon.  47,1%  of  adult  ticks  were  identified  as  Amblyomma variegatum,  which  is  a  known  vector  that  can  transmit  rickettsiae  to  humans  on  the  African continent.Riphicephalus  spp.,  Hyalomma  spp. and Boophilus  spp.  were also  identified.  The presence of rickettsial DNA was investigated in Ambylomma variegatum ticks using both real-time and conventional PCR assays for the rickettsial ompB gene.

Results and Discussion: 

From  149  Amblyomma  variegatum  ticks  tested,  85  (57 %)  were  positive  for  rickettsial DNA.  OmpB  sequencing  showed  a  high  degree  of  conservation  and homology  with  deposited sequences of R. africae, which were previously detected in ticks from other regions of Cameroon. R.  africae  are  presented  in  Ambylomma  ticks  from  the  Adamawa, Cameroon. Ambylomma variegatum is a potential vector of spotted fevers in Cameroon. R. africae should be considered by physicians in patients with febrile illness and typical skin rashes.

 

Awa DN1, Adakal H2, Luogbou ND3, Wachong KH3, Leinyuy I3, Achukwi MD1.

Cattle ticks in Cameroon: is Rhipicephalus (Boophilus) microplus absent in Cameroon and the Central African region? Ticks Tick Borne Dis. 2015 Mar;6(2):117-22. doi: 10.1016/j.ttbdis.2014.10.005. Epub 2015 Jan 7

  • 1IRAD, Bambui, PO Box 51, Bamenda, Cameroon. (Now at TOZARD PO Box 59 Bambili-Bamenda Cameroon.
  • 2CIRDES, Unit© de Recherche sur les Bases Biologiques de la lutte Int©gr©e (URBIO), 01 BP 454 Bobo-Dioulasso 01, Burkina Faso.

Introduction

In most parts of the world, ticks are rapidly developing resistance to commonly used acaricides thus rendering control difficult. This constraint is further compounded by the introduction of new species in areas where they did not exist before. Such is the case with the introduction into and rapid spread of Rhipicephalus (Boophilus) microplus in some countries of West Africa. With the looming threat of its further spread in the region, the objective of the present study was to update knowledge on cattle ticks in Cameroon.

Results and Discussions: Among 19,189 ticks collected monthly from 60 animals in 5 herds from March 2012 to February 2013, Rh. (B.) decoloratus was the most abundant species with a relative prevalence of 62.2%, followed by Amblyomma variegatum (28.4%), Rh. (B.) annulatus (0.2%), Rh. (B.) geigyi (0.03%), other Rhipicephalus spp. (8.4%) and Hyalomma spp. (0.3%). Rh. (B.) decoloratus and A. variegatum were also the most widely distributed in space. Infestation rate was generally high, with average tick count/animal of about 80 during peak periods. Tick distribution and abundance in the different sites was as varied as the underlying factors, among which the most important were management systems and climatic factors. The effects of rainfall and temperature were confounded by other factors and difficult to evaluate. However, it appears tick development depends among other factors, on a humidity threshold, above which there is not much more effect. Rh. microplus was not found during this study, but more extensive tick collections have to be done to confirm this. In conclusion, cattle tick infestation in Cameroon remains an important cause for concern. Farmers need assistance in the use and management of acaricides in order to increase their efficiency and reduce the development of resistance. Although Rh. microplus was not found, its introduction from other West African countries is imminent if adequate measures, especially in the control and limitation of animal movements, are not taken. Rh. Microplus has been reported in Ivory Coast, Burkina Faso, Benin etc.

 

Achukwi Mbunkah Daniel,1, 2* Harnett William,2 Enyong Peter3 & Renz Alfons4. Successful vaccination against Onchocerca ochengi infestation in cattle using live Onchocerca volvulus infective larvae. Parasite Immunology, 2007, 29, 113 “116 DOI: 10.1111/j.1365-3024.2006.00917.x

 

1Institute of Agricultural Research for Development, Wakwa Regional Centre, P. O. Box 65 Ngaoundere, Cameroon.

2Strathclyde University, Department of Immunology, 31 Taylor street, Glasgow, G4 ONR,   U.K

 3Medical Research Centre (IMPM) Kumba, Cameroon.

 4University of T¼bingen, Tierphysiologisches Institut, Auf der Morgenstelle 28, 72076 ¼bingen, Germany.

*Coresponding author

Abstract: Epidemiological evidence has led to the hypothesis that the concurrent and predominant transmission of Onchocerca ochengi by Simulium damnosum s.l. in sub-saharan Africa could lead to the protection of humans against onchocerciasis caused by Onchocerca volvulus (zooprophylaxis). To gain support for this hypothesis, we investigated whether exposure to O. volvulus could protect cattle from O. ochengi. Gudali calves were vaccinated with live O. volvulus infective larvae and subsequently challenged with O. ochengi infective larvae whilst raised in a fly-proof house. Post-challenge adult parasite and microfilaria development, IgG1 and lgG2 subclass antibodies response to Ov10/Ov11 recombinant Onchocerca antigens and peripheral blood lymphocyte proliferative responses to O. ochengi crude antigens were studied over a one-year period. The vaccinated-challenged animals had 83 to 87% less adult O. ochengi parasites than non-vaccinated-challenged animals. IgG1 and lgG2 antibodies to Ov10/Ov11 recombinant Onchocerca antigens were invoked by non-vaccinated-challenged animals but not by most (80%) of the vaccinated-challenged animals. These findings support the idea of cross protection (zooprophylaxis) due to inoculation of humans with O. ochengi infective larvae under natural transmission conditions in endemic areas.  Key words: Vaccination, Cattle, Onchocerca ochengi, Onchocerca volvulus, infective larvae, Lymphocytes, IgG subclass antibodies, Recombinant O. volvulus antigens.

 

Eberle R, Brattig N, Trusch M, Schlter H, Achukwi MD, Eisenbarth A, Renz A, Liebau E, Perbandt M, Betzel C.  Isolation, identification and functional profile of excretory-secretory peptides from Onchocerca ochengi.  Acta Trop. 2014 Dec 3. pii: S0001-706X(14)00384-2. doi: 10.1016/j.actatropica.2014.11.015.

Abstract: Parasitic helminthes excrete or secrete a variety of functional molecules into the internal milieu of their mammalian hosts and arthropod vectors which reveal distinct immunomodulatory and other biological activities. We identified and initially characterized the low molecular weight peptide composition of the secretome from the filarial parasite Onchocerca ochengi. A total of 85 peptides were purified by liquid chromatography and further characterized by mass spectrometry. 72 of these peptides were derived from already described Onchocerca proteins and 13 peptide sequences are included in the sequence of uncharacterized proteins. Three peptides, similar to host defense peptides, revealed antibacterial activity. The present analysis confirms the putative involvement of low molecular weight compounds in the parasite-host cross-talk.  Copyright © 2014. Published by Elsevier B.V. KEYWORDS: Antibacterial activity; Excretory “secretory products; Filaria; Functional peptides; Onchocerca