The suitability of several aquatic snails as intermediate hosts for Angiostrongylus cantonensis

Steinmann

et al. 2011

Freshwater Biology

Summary 1. Only few freshwater snail species transmit the rat lungworm Angiostrongylus cantonensis, which is partially explained by the low likelihood of contact between snails and infected rat faeces. The snail Pomacea canaliculata was introduced into China in 1981 and has become the key intermediate host for A. cantonensis. Thus far, the snail has been recorded in 13 provinces of southern China. 2. We developed a biological model and assessed potential impacts of climate change on the distribution of P. canaliculata and hence the transmission of A. cantonensis. Mean January temperature and snail generation intensity (generation number) were identified as the key factors determining P. canaliculata distribution. Our models predict an increase of 56.9% for the ‘spread’ and a decrease of 40.9% for the ‘establishment’ regions (‘spread’ and ‘establishment’ defined according to a national sampling survey) by the 2030s relative to the present day. 3. Key determinants of A. cantonensis transmission were identified as the generation intensity in the intermediate host, the longevity of A. cantonensis‐infected rats and the dormant period of P. canaliculata. Transmission of A. cantonensis occurs only in areas where the snail’s dormant period is <173.2 days. The potential endemic area of A. cantonensis is predicted to double by the 2030s relative to the present day. 4. The tight fit of our model predictions with data derived from a national sampling survey suggests that biological models hold promise for assessing potential impacts of climate change on infectious diseases once key determinants have been established. Geographical variation analysis may offer an approach to identify areas prone to the spread of vectors, intermediate hosts and parasites in a future warmer China and elsewhere.

“…While several freshwater snail species are susceptible to this nematode (Chang et al. , 1968; Yousif & Lammler, 1975; Lv et al. , 2006a), natural infections are rare (Lv et al.…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The emergence of angiostrongyliasis in the People’s Republic of China: the interplay between invasive snails, climate change and transmission dynamics

Steinmann

et al. 2011

Freshwater Biology

“…We found a threshold temperature of 15°C and a thermal constant of 262.5 degree-days. According to the results of an experiment reported by Yousif and Lammler (1975) (Halvorsen and Skorping 1982;Kutz et al 2001). Therefore, the different intermediate host may be the main reason for the higher thermal constant observed in our experiment.…”

Section: Development-time Curvementioning

confidence: 99%

“…We considered the developmental stage of larvae recovered from ctenidia and lung tissues as representative for the average development of A. cantonensis larvae in P. canaliculata. However, other researchers determined the developmental time by assessing all larvae recovered from the intermediate host (Ishii 1984), while still others considered the first appearance of a specific larval stage (Yousif and Lammler 1975). Our choice to concentrate on larvae from ctenidia and lung tissues only was based on the following reasoning.…”

Section: Development-time Curvementioning

confidence: 99%

The effect of temperature on the development of Angiostrongylus cantonensis (Chen 1935) in Pomacea canaliculata (Lamarck 1822)

Zhou

et al. 2006

Parasitol Res

Angiostrongyliasis cantonensis, clinically presented as eosinophilic meningitis, is a snail-borne parasitic disease. We studied the effects of different temperatures on the larval development of Angiostrongylus cantonensis in the freshwater snail Pomacea canaliculata. Six groups of snails were infected and each group was cultured under different temperature conditions. At predefined intervals, four snails from each group were dissected to examine the larval development. The development-time curve of each group was drawn according to the fraction of third-stage larvae present. The developmental time was defined as the time needed until 50% of the first-stage larvae developed into third-stage larvae. A linear regression model was established based on the time (D; in days) and the corresponding temperature (T; in degrees Celsius): DT = 15.04 x D + 262.53. The threshold temperature for larval development was 15.04 degrees C and the thermal constant was 262.53 degree-days. These parameters could be helpful in estimating the number of parasite generations in a year and the impact of climate change on the distribution of A. cantonensis.

“…require intermediate hosts to complete their life cycle (Anderson 2000). Terrestrial mollusks, such as snails and slugs, normally play this role, but some freshwater snails have been found to be particularly important for the transmission of angiostrongyliasis (Yousif and Lammler 1975;Morley 2006;Lv et al 2008Lv et al , 2009a. Most of them are highly specific with regard to their definitive rodent host species and even intermediate mollusk hosts, althouth cross infections have been observed (Lv et al 2008).…”

Section: Introductionmentioning

confidence: 96%

The complete mitochondrial genome of the rodent intra-arterial nematodes Angiostrongylus cantonensis and Angiostrongylus costaricensis

et al. 2012

Parasitol Res

The two rodent intra-arterial nematodes, Angiostrongylus cantonensis and Angiostrongylus costaricensis, can cause human ill-health. The present study aimed to characterize and compare the mitochondrial (mt) genomes of these two species, and clarify their phylogenetic relationship and the position in the phylum Nematoda. The complete mt genomes of A. cantonensis and A. costaricensis are 13,497 and 13,585 bp in length, respectively. Hence, they are the smallest in the class of Chromadorea characterized thus far. Like many nematode species in the class of Chromadorea, they encode 12 proteins, 22 transfer RNAs, and two ribosomal RNAs. All genes are located on the same strand. Nucleotide identity of the two mt genomes is 81.6%, ranging from 77.7% to 87.1% in individual gene pairs. Our mt genome-wide analysis identified three major gene arrangement patterns (II-1, II-2, and II-3) from 48 nematode mt genomes. Both patterns II-1 and II-2 are distinct from pattern II-3, which covers the Spirurida, supporting a closer relationship between Ascaridida and Strongylida rather than Spirurida. Thymine (T) was highly concentrated on coding strands in Chromadorea, but balanced between the two strands in Enoplea, probably due to the gene arrangement pattern. Interestingly, the gene arrangement pattern of mt genomes and phylogenetic analysis based on concatenated amino acids indicated a closer relationship between the order Ascaridida and Rhabditida rather than Spirurida as indicated in previous studies. These discrepancies call for new research, reassessing the position of the order of Ascaridida in the phylogenetic tree. Once consolidated, the findings are important for population genetic studies and target identification.